API Documentation

Providers module

class skosprovider_sqlalchemy.providers.SQLAlchemyProvider(metadata, session, **kwargs)[source]

A skosprovider.providers.VocabularyProvider that uses SQLAlchemy as backend.

expand_strategy = 'recurse'

Determines how the expand method will operate. Options are:

  • recurse: Determine all narrower concepts by recursivly querying the database. Can take a long time for concepts that are at the top of a large hierarchy.
  • visit: Query the database’s Visitation table. This table contains a nested set representation of each conceptscheme. Actually creating the data in this table needs to be scheduled.

Get all information on a concept or collection, based on a URI.

This method will only find concepts or collections whose URI is actually stored in the database. It will not find anything that has no URI in the database, but does have a matching URI after generation.

Return type:skosprovider.skos.Concept or skosprovider.skos.Collection or False if the concept or collection is unknown to the provider.
get_children_display(id, **kwargs)[source]

Return a list of concepts or collections that should be displayed under this concept or collection.

Parameters:id – A concept or collection id.
Return type:A list of concepts and collections. For each an id is present and a label. The label is determined by looking at the **kwargs parameter, the default language of the provider and falls back to en if nothing is present. If the id does not exist, return False.

Returns all concepts or collections that form the top-level of a display hierarchy.

As opposed to the get_top_concepts(), this method can possibly return both concepts and collections.

Return type:Returns a list of concepts and collections. For each an id is present and a label. The label is determined by looking at the **kwargs parameter, the default language of the provider and falls back to en if nothing is present.

Models module

class skosprovider_sqlalchemy.models.Collection(**kwargs)[source]

A collection as know by SKOS.

class skosprovider_sqlalchemy.models.Concept(**kwargs)[source]

A concept as know by SKOS.

class skosprovider_sqlalchemy.models.ConceptScheme(**kwargs)[source]

A SKOS conceptscheme.

class skosprovider_sqlalchemy.models.Initialiser(session)[source]

Initialises a database.

Adds necessary values for labelType, noteType and language to the database.

The list of languages added by default is very small and will probably need to be expanded for your local needs.


Initialise all objects (labeltype, notetype, language).


Initialise the labeltypes.


Initialise the languages.

Only adds a small set of languages. Will probably not be sufficient for most use cases.


Initialise the matchtypes.


Initialise the notetypes.

class skosprovider_sqlalchemy.models.Label(label, labeltype_id=u'prefLabel', language_id=None)[source]

A label for a Concept, Collection or ConceptScheme.

class skosprovider_sqlalchemy.models.LabelType(name, description)[source]

A labelType according to SKOS.

class skosprovider_sqlalchemy.models.Language(id, name)[source]

A Language.

class skosprovider_sqlalchemy.models.Match(**kwargs)[source]

A match between a Concept in one ConceptScheme and those in another one.

class skosprovider_sqlalchemy.models.MatchType(name, description)[source]

A matchType according to SKOS.

class skosprovider_sqlalchemy.models.Note(note, notetype_id, language_id)[source]

A note for a Concept, Collection or ConceptScheme.

class skosprovider_sqlalchemy.models.NoteType(name, description)[source]

A noteType according to SKOS.

class skosprovider_sqlalchemy.models.Thing(**kwargs)[source]

Abstract class for both Concept and Collection.

class skosprovider_sqlalchemy.models.Visitation(**kwargs)[source]

Holds several nested sets.

The visitation object and table hold several nested sets. Each skosprovider_sqlalchemy.models.Visitation holds the positional information for one conceptplacement in a certain nested set.

Each conceptscheme gets its own separate nested set.

skosprovider_sqlalchemy.models.label(labels=, []language=u'any')[source]

Provide a label for a list of labels.

The items in the list of labels are assumed to be instances of Label.

This method tries to find a label by looking if there’s a pref label for the specified language. If there’s no pref label, it looks for an alt label. It disregards hidden labels.

While matching languages, preference will be given to exact matches. But, if no exact match is present, an inexact match will be attempted. This might be because a label in language nl-BE is being requested, but only nl or even nl-NL is present. Similarly, when requesting nl, a label with language nl-NL or even nl-Latn-NL will also be considered, providing no label is present that has an exact match with the requested language.

If language ‘any’ was specified, all labels will be considered, regardless of language.

To find a label without a specified language, pass None as language.

If a language or None was specified, and no label could be found, this method will automatically try to find a label in some other language.

Finally, if no label could be found, None is returned.

  • labels (list) – A list of labels.
  • language (str) – The language for which a label should preferentially be returned. This should be a valid IANA language tag.
Return type:

A Label or None if no label could be found.

skosprovider_sqlalchemy.models.related_concepts_append_listener(target, value, initiator)[source]

Listener that ensures related concepts have a bidirectional relationship.

skosprovider_sqlalchemy.models.related_concepts_remove_listener(target, value, initiator)[source]

Listener to remove a related concept from both ends of the relationship.

skosprovider_sqlalchemy.models.relationship(argument, secondary=None, primaryjoin=None, secondaryjoin=None, foreign_keys=None, uselist=None, order_by=False, backref=None, back_populates=None, post_update=False, cascade=False, extension=None, viewonly=False, lazy=True, collection_class=None, passive_deletes=False, passive_updates=True, remote_side=None, enable_typechecks=True, join_depth=None, comparator_factory=None, single_parent=False, innerjoin=False, distinct_target_key=None, doc=None, active_history=False, cascade_backrefs=True, load_on_pending=False, strategy_class=None, _local_remote_pairs=None, query_class=None, info=None)

Provide a relationship between two mapped classes.

This corresponds to a parent-child or associative table relationship. The constructed class is an instance of RelationshipProperty.

A typical relationship(), used in a classical mapping:

mapper(Parent, properties={
  'children': relationship(Child)

Some arguments accepted by relationship() optionally accept a callable function, which when called produces the desired value. The callable is invoked by the parent Mapper at “mapper initialization” time, which happens only when mappers are first used, and is assumed to be after all mappings have been constructed. This can be used to resolve order-of-declaration and other dependency issues, such as if Child is declared below Parent in the same file:

mapper(Parent, properties={
    "children":relationship(lambda: Child,
                        order_by=lambda: Child.id)

When using the declarative_toplevel extension, the Declarative initializer allows string arguments to be passed to relationship(). These string arguments are converted into callables that evaluate the string as Python code, using the Declarative class-registry as a namespace. This allows the lookup of related classes to be automatic via their string name, and removes the need to import related classes at all into the local module space:

from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()

class Parent(Base):
    __tablename__ = 'parent'
    id = Column(Integer, primary_key=True)
    children = relationship("Child", order_by="Child.id")

See also

relationship_config_toplevel - Full introductory and reference documentation for relationship().

orm_tutorial_relationship - ORM tutorial introduction.

  • argument

    a mapped class, or actual Mapper instance, representing the target of the relationship.

    :paramref:`~.relationship.argument` may also be passed as a callable function which is evaluated at mapper initialization time, and may be passed as a Python-evaluable string when using Declarative.

    See also

    declarative_configuring_relationships - further detail on relationship configuration when using Declarative.

  • secondary

    for a many-to-many relationship, specifies the intermediary table, and is typically an instance of Table. In less common circumstances, the argument may also be specified as an Alias construct, or even a Join construct.

    :paramref:`~.relationship.secondary` may also be passed as a callable function which is evaluated at mapper initialization time. When using Declarative, it may also be a string argument noting the name of a Table that is present in the MetaData collection associated with the parent-mapped Table.

    The :paramref:`~.relationship.secondary` keyword argument is typically applied in the case where the intermediary Table is not otherwise exprssed in any direct class mapping. If the “secondary” table is also explicitly mapped elsewhere (e.g. as in association_pattern), one should consider applying the :paramref:`~.relationship.viewonly` flag so that this relationship() is not used for persistence operations which may conflict with those of the association object pattern.

    See also

    relationships_many_to_many - Reference example of “many to many”.

    orm_tutorial_many_to_many - ORM tutorial introduction to many-to-many relationships.

    self_referential_many_to_many - Specifics on using many-to-many in a self-referential case.

    declarative_many_to_many - Additional options when using Declarative.

    association_pattern - an alternative to :paramref:`~.relationship.secondary` when composing association table relationships, allowing additional attributes to be specified on the association table.

    composite_secondary_join - a lesser-used pattern which in some cases can enable complex relationship() SQL conditions to be used.

    New in version 0.9.2: :paramref:`~.relationship.secondary` works more effectively when referring to a Join instance.

  • active_history=False – When True, indicates that the “previous” value for a many-to-one reference should be loaded when replaced, if not already loaded. Normally, history tracking logic for simple many-to-ones only needs to be aware of the “new” value in order to perform a flush. This flag is available for applications that make use of attributes.get_history() which also need to know the “previous” value of the attribute.
  • backref

    indicates the string name of a property to be placed on the related mapper’s class that will handle this relationship in the other direction. The other property will be created automatically when the mappers are configured. Can also be passed as a backref() object to control the configuration of the new relationship.

    See also

    relationships_backref - Introductory documentation and examples.

    :paramref:`~.relationship.back_populates` - alternative form of backref specification.

    backref() - allows control over relationship() configuration when using :paramref:`~.relationship.backref`.

  • back_populates

    Takes a string name and has the same meaning as :paramref:`~.relationship.backref`, except the complementing property is not created automatically, and instead must be configured explicitly on the other mapper. The complementing property should also indicate :paramref:`~.relationship.back_populates` to this relationship to ensure proper functioning.

    See also

    relationships_backref - Introductory documentation and examples.

    :paramref:`~.relationship.backref` - alternative form of backref specification.

  • cascade

    a comma-separated list of cascade rules which determines how Session operations should be “cascaded” from parent to child. This defaults to False, which means the default cascade should be used - this default cascade is "save-update, merge".

    The available cascades are save-update, merge, expunge, delete, delete-orphan, and refresh-expire. An additional option, all indicates shorthand for "save-update, merge, refresh-expire, expunge, delete", and is often used as in "all, delete-orphan" to indicate that related objects should follow along with the parent object in all cases, and be deleted when de-associated.

    See also

    unitofwork_cascades - Full detail on each of the available cascade options.

    tutorial_delete_cascade - Tutorial example describing a delete cascade.

  • cascade_backrefs=True

    a boolean value indicating if the save-update cascade should operate along an assignment event intercepted by a backref. When set to False, the attribute managed by this relationship will not cascade an incoming transient object into the session of a persistent parent, if the event is received via backref.

    See also

    backref_cascade - Full discussion and examples on how the :paramref:`~.relationship.cascade_backrefs` option is used.

  • collection_class

    a class or callable that returns a new list-holding object. will be used in place of a plain list for storing elements.

    See also

    custom_collections - Introductory documentation and examples.

  • comparator_factory

    a class which extends RelationshipProperty.Comparator which provides custom SQL clause generation for comparison operations.

    See also

    PropComparator - some detail on redefining comparators at this level.

    custom_comparators - Brief intro to this feature.

  • distinct_target_key=None

    Indicate if a “subquery” eager load should apply the DISTINCT keyword to the innermost SELECT statement. When left as None, the DISTINCT keyword will be applied in those cases when the target columns do not comprise the full primary key of the target table. When set to True, the DISTINCT keyword is applied to the innermost SELECT unconditionally.

    It may be desirable to set this flag to False when the DISTINCT is reducing performance of the innermost subquery beyond that of what duplicate innermost rows may be causing.

    New in version 0.8.3: - :paramref:`~.relationship.distinct_target_key` allows the subquery eager loader to apply a DISTINCT modifier to the innermost SELECT.

    Changed in version 0.9.0: - :paramref:`~.relationship.distinct_target_key` now defaults to None, so that the feature enables itself automatically for those cases where the innermost query targets a non-unique key.

    See also

    loading_toplevel - includes an introduction to subquery eager loading.

  • doc – docstring which will be applied to the resulting descriptor.
  • extension

    an AttributeExtension instance, or list of extensions, which will be prepended to the list of attribute listeners for the resulting descriptor placed on the class.

    Deprecated since version 0.7: Please see AttributeEvents.

  • foreign_keys

    a list of columns which are to be used as “foreign key” columns, or columns which refer to the value in a remote column, within the context of this relationship() object’s :paramref:`~.relationship.primaryjoin` condition. That is, if the :paramref:`~.relationship.primaryjoin` condition of this relationship() is a.id == b.a_id, and the values in b.a_id are required to be present in a.id, then the “foreign key” column of this relationship() is b.a_id.

    In normal cases, the :paramref:`~.relationship.foreign_keys` parameter is not required. relationship() will automatically determine which columns in the :paramref:`~.relationship.primaryjoin` conditition are to be considered “foreign key” columns based on those Column objects that specify ForeignKey, or are otherwise listed as referencing columns in a ForeignKeyConstraint construct. :paramref:`~.relationship.foreign_keys` is only needed when:

    1. There is more than one way to construct a join from the local table to the remote table, as there are multiple foreign key references present. Setting foreign_keys will limit the relationship() to consider just those columns specified here as “foreign”.

      Changed in version 0.8: A multiple-foreign key join ambiguity can be resolved by setting the :paramref:`~.relationship.foreign_keys` parameter alone, without the need to explicitly set :paramref:`~.relationship.primaryjoin` as well.

    2. The Table being mapped does not actually have ForeignKey or ForeignKeyConstraint constructs present, often because the table was reflected from a database that does not support foreign key reflection (MySQL MyISAM).
    3. The :paramref:`~.relationship.primaryjoin` argument is used to construct a non-standard join condition, which makes use of columns or expressions that do not normally refer to their “parent” column, such as a join condition expressed by a complex comparison using a SQL function.

    The relationship() construct will raise informative error messages that suggest the use of the :paramref:`~.relationship.foreign_keys` parameter when presented with an ambiguous condition. In typical cases, if relationship() doesn’t raise any exceptions, the :paramref:`~.relationship.foreign_keys` parameter is usually not needed.

    :paramref:`~.relationship.foreign_keys` may also be passed as a callable function which is evaluated at mapper initialization time, and may be passed as a Python-evaluable string when using Declarative.

    See also



    foreign() - allows direct annotation of the “foreign” columns within a :paramref:`~.relationship.primaryjoin` condition.

    New in version 0.8: The foreign() annotation can also be applied directly to the :paramref:`~.relationship.primaryjoin` expression, which is an alternate, more specific system of describing which columns in a particular :paramref:`~.relationship.primaryjoin` should be considered “foreign”.

  • info

    Optional data dictionary which will be populated into the MapperProperty.info attribute of this object.

    New in version 0.8.

  • innerjoin=False

    when True, joined eager loads will use an inner join to join against related tables instead of an outer join. The purpose of this option is generally one of performance, as inner joins generally perform better than outer joins.

    This flag can be set to True when the relationship references an object via many-to-one using local foreign keys that are not nullable, or when the reference is one-to-one or a collection that is guaranteed to have one or at least one entry.

    If the joined-eager load is chained onto an existing LEFT OUTER JOIN, innerjoin=True will be bypassed and the join will continue to chain as LEFT OUTER JOIN so that the results don’t change. As an alternative, specify the value "nested". This will instead nest the join on the right side, e.g. using the form “a LEFT OUTER JOIN (b JOIN c)”.

    New in version 0.9.4: Added innerjoin="nested" option to support nesting of eager “inner” joins.

    See also

    what_kind_of_loading - Discussion of some details of various loader options.

    :paramref:`.joinedload.innerjoin` - loader option version

  • join_depth

    when non-None, an integer value indicating how many levels deep “eager” loaders should join on a self-referring or cyclical relationship. The number counts how many times the same Mapper shall be present in the loading condition along a particular join branch. When left at its default of None, eager loaders will stop chaining when they encounter a the same target mapper which is already higher up in the chain. This option applies both to joined- and subquery- eager loaders.

    See also

    self_referential_eager_loading - Introductory documentation and examples.

  • lazy=’select’

    specifies how the related items should be loaded. Default value is select. Values include:

    • select - items should be loaded lazily when the property is first accessed, using a separate SELECT statement, or identity map fetch for simple many-to-one references.
    • immediate - items should be loaded as the parents are loaded, using a separate SELECT statement, or identity map fetch for simple many-to-one references.
    • joined - items should be loaded “eagerly” in the same query as that of the parent, using a JOIN or LEFT OUTER JOIN. Whether the join is “outer” or not is determined by the :paramref:`~.relationship.innerjoin` parameter.
    • subquery - items should be loaded “eagerly” as the parents are loaded, using one additional SQL statement, which issues a JOIN to a subquery of the original statement, for each collection requested.
    • noload - no loading should occur at any time. This is to support “write-only” attributes, or attributes which are populated in some manner specific to the application.
    • dynamic - the attribute will return a pre-configured Query object for all read operations, onto which further filtering operations can be applied before iterating the results. See the section dynamic_relationship for more details.
    • True - a synonym for ‘select’
    • False - a synonym for ‘joined’
    • None - a synonym for ‘noload’

    See also

    /orm/loading - Full documentation on relationship loader configuration.

    dynamic_relationship - detail on the dynamic option.

  • load_on_pending=False

    Indicates loading behavior for transient or pending parent objects.

    When set to True, causes the lazy-loader to issue a query for a parent object that is not persistent, meaning it has never been flushed. This may take effect for a pending object when autoflush is disabled, or for a transient object that has been “attached” to a Session but is not part of its pending collection.

    The :paramref:`~.relationship.load_on_pending` flag does not improve behavior when the ORM is used normally - object references should be constructed at the object level, not at the foreign key level, so that they are present in an ordinary way before a flush proceeds. This flag is not not intended for general use.

    See also

    Session.enable_relationship_loading() - this method establishes “load on pending” behavior for the whole object, and also allows loading on objects that remain transient or detached.

  • order_by

    indicates the ordering that should be applied when loading these items. :paramref:`~.relationship.order_by` is expected to refer to one of the Column objects to which the target class is mapped, or the attribute itself bound to the target class which refers to the column.

    :paramref:`~.relationship.order_by` may also be passed as a callable function which is evaluated at mapper initialization time, and may be passed as a Python-evaluable string when using Declarative.

  • passive_deletes=False

    Indicates loading behavior during delete operations.

    A value of True indicates that unloaded child items should not be loaded during a delete operation on the parent. Normally, when a parent item is deleted, all child items are loaded so that they can either be marked as deleted, or have their foreign key to the parent set to NULL. Marking this flag as True usually implies an ON DELETE <CASCADE|SET NULL> rule is in place which will handle updating/deleting child rows on the database side.

    Additionally, setting the flag to the string value ‘all’ will disable the “nulling out” of the child foreign keys, when there is no delete or delete-orphan cascade enabled. This is typically used when a triggering or error raise scenario is in place on the database side. Note that the foreign key attributes on in-session child objects will not be changed after a flush occurs so this is a very special use-case setting.

    See also

    passive_deletes - Introductory documentation and examples.

  • passive_updates=True

    Indicates loading and INSERT/UPDATE/DELETE behavior when the source of a foreign key value changes (i.e. an “on update” cascade), which are typically the primary key columns of the source row.

    When True, it is assumed that ON UPDATE CASCADE is configured on the foreign key in the database, and that the database will handle propagation of an UPDATE from a source column to dependent rows. Note that with databases which enforce referential integrity (i.e. PostgreSQL, MySQL with InnoDB tables), ON UPDATE CASCADE is required for this operation. The relationship() will update the value of the attribute on related items which are locally present in the session during a flush.

    When False, it is assumed that the database does not enforce referential integrity and will not be issuing its own CASCADE operation for an update. The relationship() will issue the appropriate UPDATE statements to the database in response to the change of a referenced key, and items locally present in the session during a flush will also be refreshed.

    This flag should probably be set to False if primary key changes are expected and the database in use doesn’t support CASCADE (i.e. SQLite, MySQL MyISAM tables).

    See also

    passive_updates - Introductory documentation and examples.

    :paramref:`.mapper.passive_updates` - a similar flag which takes effect for joined-table inheritance mappings.

  • post_update

    this indicates that the relationship should be handled by a second UPDATE statement after an INSERT or before a DELETE. Currently, it also will issue an UPDATE after the instance was UPDATEd as well, although this technically should be improved. This flag is used to handle saving bi-directional dependencies between two individual rows (i.e. each row references the other), where it would otherwise be impossible to INSERT or DELETE both rows fully since one row exists before the other. Use this flag when a particular mapping arrangement will incur two rows that are dependent on each other, such as a table that has a one-to-many relationship to a set of child rows, and also has a column that references a single child row within that list (i.e. both tables contain a foreign key to each other). If a flush operation returns an error that a “cyclical dependency” was detected, this is a cue that you might want to use :paramref:`~.relationship.post_update` to “break” the cycle.

    See also

    post_update - Introductory documentation and examples.

  • primaryjoin

    a SQL expression that will be used as the primary join of this child object against the parent object, or in a many-to-many relationship the join of the primary object to the association table. By default, this value is computed based on the foreign key relationships of the parent and child tables (or association table).

    :paramref:`~.relationship.primaryjoin` may also be passed as a callable function which is evaluated at mapper initialization time, and may be passed as a Python-evaluable string when using Declarative.

    See also


  • remote_side

    used for self-referential relationships, indicates the column or list of columns that form the “remote side” of the relationship.

    :paramref:`.relationship.remote_side` may also be passed as a callable function which is evaluated at mapper initialization time, and may be passed as a Python-evaluable string when using Declarative.

    Changed in version 0.8: The remote() annotation can also be applied directly to the primaryjoin expression, which is an alternate, more specific system of describing which columns in a particular primaryjoin should be considered “remote”.

    See also

    self_referential - in-depth explanation of how :paramref:`~.relationship.remote_side` is used to configure self-referential relationships.

    remote() - an annotation function that accomplishes the same purpose as :paramref:`~.relationship.remote_side`, typically when a custom :paramref:`~.relationship.primaryjoin` condition is used.

  • query_class

    a Query subclass that will be used as the base of the “appender query” returned by a “dynamic” relationship, that is, a relationship that specifies lazy="dynamic" or was otherwise constructed using the orm.dynamic_loader() function.

    See also

    dynamic_relationship - Introduction to “dynamic” relationship loaders.

  • secondaryjoin

    a SQL expression that will be used as the join of an association table to the child object. By default, this value is computed based on the foreign key relationships of the association and child tables.

    :paramref:`~.relationship.secondaryjoin` may also be passed as a callable function which is evaluated at mapper initialization time, and may be passed as a Python-evaluable string when using Declarative.

    See also


  • single_parent

    when True, installs a validator which will prevent objects from being associated with more than one parent at a time. This is used for many-to-one or many-to-many relationships that should be treated either as one-to-one or one-to-many. Its usage is optional, except for relationship() constructs which are many-to-one or many-to-many and also specify the delete-orphan cascade option. The relationship() construct itself will raise an error instructing when this option is required.

    See also

    unitofwork_cascades - includes detail on when the :paramref:`~.relationship.single_parent` flag may be appropriate.

  • uselist

    a boolean that indicates if this property should be loaded as a list or a scalar. In most cases, this value is determined automatically by relationship() at mapper configuration time, based on the type and direction of the relationship - one to many forms a list, many to one forms a scalar, many to many is a list. If a scalar is desired where normally a list would be present, such as a bi-directional one-to-one relationship, set :paramref:`~.relationship.uselist` to False.

    The :paramref:`~.relationship.uselist` flag is also available on an existing relationship() construct as a read-only attribute, which can be used to determine if this relationship() deals with collections or scalar attributes:

    >>> User.addresses.property.uselist

    See also

    relationships_one_to_one - Introduction to the “one to one” relationship pattern, which is typically when the :paramref:`~.relationship.uselist` flag is needed.

  • viewonly=False – when set to True, the relationship is used only for loading objects, and not for any persistence operation. A relationship() which specifies :paramref:`~.relationship.viewonly` can work with a wider range of SQL operations within the :paramref:`~.relationship.primaryjoin` condition, including operations that feature the use of a variety of comparison operators as well as SQL functions such as cast(). The :paramref:`~.relationship.viewonly` flag is also of general use when defining any kind of relationship() that doesn’t represent the full set of related objects, to prevent modifications of the collection from resulting in persistence operations.

Utils module

class skosprovider_sqlalchemy.utils.VisitationCalculator(session)[source]

Generates a nested set for a conceptscheme.


Visit a skosprovider_sqlalchemy.models.Conceptscheme and calculate a nested set representation.

Parameters:conceptscheme – A skosprovider_sqlalchemy.models.Conceptscheme for which the nested set will be calculated.
skosprovider_sqlalchemy.utils.import_provider(provider, conceptscheme, session)[source]

Import a provider into a SQLAlchemy database.

  • provider – The skosprovider.providers.VocabularyProvider to import. Since the SQLAlchemy backend uses integers as keys, this backend should have id values that can be cast to int.
  • conceptscheme – A skosprovider_sqlalchemy.models.Conceptscheme to import the provider into. This should be an empty scheme so that there are no possible id clashes.
  • session – A sqlalchemy.orm.session.Session.