code: func (db *nodeDB) localEndpoint(id NodeID) *rpcEndpoint {
  	var ep rpcEndpoint
  	if err := db.fetchRLP(makeKey(id, nodeDBDiscoverLocalEndpoint), &ep); err != nil {
  		return nil
  	}
  	return &ep
  }
docs: // localEndpoint returns the last local endpoint communicated to the
  // given remote node.