docs: def connection(self):
          """Request-bound database connection."""
          assert flask.has_request_context(), \
                 'tried to connect zodb outside request'
          if not self.is_connected:
              connector = flask.current_app.extensions['zodb']
              flask._request_ctx_stack.top.zodb_connection = connector.db.open()
              transaction.begin()
          return flask._request_ctx_stack.top.zodb_connection