docs: def connectPeer(self, peer):
          """Establish a SIGMA connection to the given peer.
  
          @param peer: a Q2QAddress of a peer which has a file that I want
  
          @return: a Deferred which fires a SigmaProtocol.
          """
          return self.conns.connectCached(endpoint.Q2QEndpoint(self.svc,
                                                               self.addr,
                                                               peer,
                                                               PROTOCOL_NAME),
                                          self.clientFactory)