public string ToString(TokenClass classNumber, int tokenNumber)
            {
                var token = "?";

                switch (classNumber)
                {
                case TokenClass.ReservedWord:
                    token = ReservedWords.ElementAt(tokenNumber);
                    break;

                case TokenClass.OperationSign:
                    token = OperationSigns.ElementAt(tokenNumber);
                    break;

                case TokenClass.Delmer:
                    token = Delmers.ElementAt(tokenNumber);
                    break;
                }

                return($"{classNumber}:{token}");
            }