docs: def _inbound(self, From, to, protocol, udp_source=None):
          """
          Implementation of L{Inbound}.
          """
          # Verify stuff!
  
          self.verifyCertificateAllowed(to, From)
          return self.service.verifyHook(From, to, protocol
                                         ).addCallback(self._inboundimpl,
                                                       From,
                                                       to,
                                                       protocol,
                                                       udp_source).addErrback(
              lambda f: f.trap(KeyError) and dict(listeners=[]))