code: def end_before(self, document_fields):
          
          query = query_mod.Query(self)
          return query.end_before(document_fields)
docs: End query before a cursor with this collection as parent.
  
          See
          :meth:`~.firestore_v1beta1.query.Query.end_before` for
          more information on this method.
  
          Args:
              document_fields (Union[~.firestore_v1beta1.\
                  document.DocumentSnapshot, dict, list, tuple]): a document
                  snapshot or a dictionary/list/tuple of fields representing a
                  query results cursor. A cursor is a collection of values that
                  represent a position in a query result set.
  
          Returns:
              ~.firestore_v1beta1.query.Query: A query with cursor.