docs: def remove_session(self, session):
          """
          :param sqlalchemy.session.Session session: Database session to remove
          """
          try:
              del session.redis
          except AttributeError:
              pass
          try:
              del session.index_new[self.cls_name]
              del session.index_dirty[self.cls_name]
              del session.index_deleted[self.cls_name]
          except (AttributeError, KeyError):
              log.warning('Removing a session that has no indexing sets.')
          self.sessions.remove(session)