code: def tor_agent(reactor, socks_endpoint, circuit=None, pool=None):
      
  
      if socks_endpoint is None:
          raise ValueError(
              "Must provide socks_endpoint as Deferred or IStreamClientEndpoint"
          )
      if circuit is not None:
          factory = _AgentEndpointFactoryForCircuit(reactor, socks_endpoint, circuit)
      else:
          factory = _AgentEndpointFactoryUsingTor(reactor, socks_endpoint)
      return Agent.usingEndpointFactory(reactor, factory, pool=pool)
docs: This is the low-level method used by
      :meth:`txtorcon.Tor.web_agent` and
      :meth:`txtorcon.Circuit.web_agent` -- probably you should call one
      of those instead.
  
      :returns: a Deferred that fires with an object that implements
          :class:`twisted.web.iweb.IAgent` and is thus suitable for passing
          to ``treq`` as the ``agent=`` kwarg. Of course can be used
          directly; see `using Twisted web cliet
          <http://twistedmatrix.com/documents/current/web/howto/client.html>`_.
  
      :param reactor: the reactor to use
  
      :param circuit: If supplied, a particular circuit to use
  
      :param socks_endpoint: Deferred that fires w/
          IStreamClientEndpoint (or IStreamClientEndpoint instance)
          which points at a SOCKS5 port of our Tor
  
      :param pool: passed on to the Agent (as ``pool=``)