code: def _get_isolated(self, hostport):
          
          assert hostport, "hostport is required"
          if hostport not in self._peers:
              # Add a peer directly from a hostport, do NOT add it to the peer
              # heap
              peer = self.peer_class(
                  tchannel=self.tchannel,
                  hostport=hostport,
              )
              self._peers[peer.hostport] = peer
  
          return self._peers[hostport]
docs: Get a Peer for the given destination for a request.
  
          A new Peer is added and returned if one does not already exist for the
          given host-port. Otherwise, the existing Peer is returned.
  
          **NOTE** new peers will not be added to the peer heap.