def close(self, **kw):

        self._closing_deferred = defer.Deferred()

        def close_command_is_queued(*args):
            return self._closing_deferred
        d = self.torstate.close_circuit(self.id, **kw)
        d.addCallback(close_command_is_queued)
        return self._closing_deferred
This asks Tor to close the underlying circuit object. See
dataset/ETHPy150Open meejah/txtorcon/txtorcon/circuit.py/Circuit.close