def query(self, **kwargs):
        """Proxy to :class:`google.cloud.datastore.query.Query`.

        Passes our ``project``.

        Using query to search a datastore:

        .. testsetup:: query

            import os
            import uuid

            from google.cloud import datastore

            unique = os.getenv('CIRCLE_BUILD_NUM', str(uuid.uuid4())[0:8])
            client = datastore.Client(namespace='ns{}'.format(unique))
            query = client.query(kind='_Doctest')

            def do_something(entity):
                pass

        .. doctest:: query

            >>> query = client.query(kind='MyKind')
            >>> query.add_filter('property', '=', 'val')

        Using the query iterator

        .. doctest:: query

            >>> query_iter = query.fetch()
            >>> for entity in query_iter:
            ...     do_something(entity)

        or manually page through results

        .. testsetup:: query-page

            import os
            import uuid

            from google.cloud import datastore
            from tests.system.test_system import Config  # system tests

            unique = os.getenv('CIRCLE_BUILD_NUM', str(uuid.uuid4())[0:8])
            client = datastore.Client(namespace='ns{}'.format(unique))

            key = client.key('_Doctest')
            entity1 = datastore.Entity(key=key)
            entity1['foo'] = 1337
            entity2 = datastore.Entity(key=key)
            entity2['foo'] = 42
            Config.TO_DELETE.extend([entity1, entity2])
            client.put_multi([entity1, entity2])

            query = client.query(kind='_Doctest')
            cursor = None

        .. doctest:: query-page

            >>> query_iter = query.fetch(start_cursor=cursor)
            >>> pages = query_iter.pages
            >>>
            >>> first_page = next(pages)
            >>> first_page_entities = list(first_page)
            >>> query_iter.next_page_token is None
            True

        :type kwargs: dict
        :param kwargs: Parameters for initializing and instance of
                       :class:`~google.cloud.datastore.query.Query`.

        :rtype: :class:`~google.cloud.datastore.query.Query`
        :returns: A query object.
        """
        if "client" in kwargs:
            raise TypeError("Cannot pass client")
        if "project" in kwargs:
            raise TypeError("Cannot pass project")
        kwargs["project"] = self.project
        if "namespace" not in kwargs:
            kwargs["namespace"] = self.namespace
        return Query(self, **kwargs)