code: func ValidTransactionTrytes(trytes Trytes) error {
  	// verifies length and trytes values
  	if !guards.IsTrytesOfExactLength(trytes, TransactionTrytesSize) {
  		return ErrInvalidTrytes
  	}
  
  	if trytes[2279:2295] != "9999999999999999" {
  		return ErrInvalidTrytes
  	}
  
  	return nil
  }
docs: // ValidTransactionTrytes checks whether the given trytes make up a valid transaction schematically.