Method dereference

pymongo/synchronous/database.py:1439–1479

Dereference a :class:`~bson.dbref.DBRef`, getting the document it points to. Raises :class:`TypeError` if `dbref` is not an instance of :class:`~bson.dbref.DBRef`. Returns a document, or ``None`` if the reference does not point to a valid document. Raises :c

(
        self,
        dbref: DBRef,
        session: Optional[ClientSession] = None,
        comment: Optional[Any] = None,
        **kwargs: Any,
    )

        return result

    def dereference(
        self,
        dbref: DBRef,
        session: Optional[ClientSession] = None,
        comment: Optional[Any] = None,
        **kwargs: Any,
    ) -> Optional[_DocumentType]:
        """Dereference a :class:`~bson.dbref.DBRef`, getting the
        document it points to.

        Raises :class:`TypeError` if `dbref` is not an instance of
        :class:`~bson.dbref.DBRef`. Returns a document, or ``None`` if
        the reference does not point to a valid document.  Raises
        :class:`ValueError` if `dbref` has a database specified that
        is different from the current database.

        :param dbref: the reference
        :param session: a
            :class:`~pymongo.client_session.ClientSession`.
        :param comment: A user-provided comment to attach to this
            command.
        :param kwargs: any additional keyword arguments
            are the same as the arguments to
            :meth:`~pymongo.collection.Collection.find`.


        .. versionchanged:: 4.1
           Added ``comment`` parameter.
        .. versionchanged:: 3.6
           Added ``session`` parameter.
        """
        if not isinstance(dbref, DBRef):
            raise TypeError("cannot dereference a %s" % type(dbref))
        if dbref.database is not None and dbref.database != self._name:
            raise ValueError(
                "trying to dereference a DBRef that points to "
                f"another database ({dbref.database!r} not {self._name!r})"
            )
        return self[dbref.collection].find_one(
            {"_id": dbref.id}, session=session, comment=comment, **kwargs
        )