code: def free(self):
          
          self._freed = True
          self._cleanup(self.cursor, self._fd)
docs: Release the results and connection lock from the TornadoSession
          object. This **must** be called after you finish processing the results
          from :py:meth:`TornadoSession.query <queries.TornadoSession.query>` or
          :py:meth:`TornadoSession.callproc <queries.TornadoSession.callproc>`
          or the connection will not be able to be reused by other asynchronous
          requests.