code: def session_update(self, session, *_):
          
          self._session_init(session)
          session.pending_write |= set(session.new)
          session.pending_update |= set(session.dirty)
          session.pending_delete |= set(session.deleted)
          self.logger.debug("%s - session_update" % session.meepo_unique_id)
docs: Record the sqlalchemy object states in the middle of session,
          prepare the events for the final pub in session_commit.