code: func (tm *transactionManager) filterOne(
  	transID string, addr *net.UDPAddr) *transaction {
  
  	trans := tm.getByTransID(transID)
  	if trans == nil || trans.node.addr.String() != addr.String() {
  		return nil
  	}
  
  	return trans
  }
docs: // transaction gets the proper transaction with whose id is transId and
  // address is addr.