Requests are passed as a list of write operation instances (
        :class:`~pymongo.operations.InsertOne`,
        :class:`~pymongo.operations.UpdateOne`,
        :class:`~pymongo.operations.UpdateMany`,
        :class:`~pymongo.operations.ReplaceOne`,
        :class:`~pymongo.operations.DeleteOne`, or
        :class:`~pymongo.operations.DeleteMany`).

          >>> for doc in db.test.find({}):
          ...     print(doc)
          ...
          {'x': 1, '_id': ObjectId('54f62e60fba5226811f634ef')}
          {'x': 1, '_id': ObjectId('54f62e60fba5226811f634f0')}
          >>> # DeleteMany, UpdateOne, and UpdateMany are also available.
          ...
          >>> from pymongo import InsertOne, DeleteOne, ReplaceOne
          >>> requests = [InsertOne({'y': 1}), DeleteOne({'x': 1}),
          ...             ReplaceOne({'w': 1}, {'z': 1}, upsert=True)]
          >>> result = db.test.bulk_write(requests)
          >>> result.inserted_count
          1
          >>> result.deleted_count
          1
          >>> result.modified_count
          0
          >>> result.upserted_ids
          {2: ObjectId('54f62ee28891e756a6e1abd5')}
          >>> for doc in db.test.find({}):
          ...     print(doc)
          ...
          {'x': 1, '_id': ObjectId('54f62e60fba5226811f634f0')}
          {'y': 1, '_id': ObjectId('54f62ee2fba5226811f634f1')}
          {'z': 1, '_id': ObjectId('54f62ee28891e756a6e1abd5')}

        :Parameters:
          - `requests`: A list of write operations (see examples above).
          - `ordered` (optional): If ``True`` (the default) requests will be
            performed on the server serially, in the order provided. If an error
            occurs all remaining operations are aborted. If ``False`` requests
            will be performed on the server in arbitrary order, possibly in
            parallel, and all operations will be attempted.
          - `bypass_document_validation`: (optional) If ``True``, allows the
            write to opt-out of document level validation. Default is
            ``False``.
          - `session` (optional): a
            :class:`~pymongo.client_session.ClientSession`.

        :Returns:
          An instance of :class:`~pymongo.results.BulkWriteResult`.

        .. seealso:: :ref:`writes-and-ids`

        .. note:: `bypass_document_validation` requires server version
          **>= 3.2**

        .. versionchanged:: 3.6
           Added ``session`` parameter.

        .. versionchanged:: 3.2
          Added bypass_document_validation support

        .. versionadded:: 3.0