def to_s
      [
        Hexnum.new(@id, 4).to_s,
        @date.utc.iso8601,
        Hexnum.new(@amount.to_i, 16),
        @prefix,
        @bnf,
        @details,
        @sign
      ].join(';')
    end
def to_s
      [
        Hexnum.new(@id, 4).to_s,
        @date.utc.iso8601,
        Hexnum.new(@amount.to_i, 16),
        @prefix,
        @bnf,
        @details,
        @sign
      ].join(';')
    end
Make a new object of this class (you must read the White Paper
 in order to understand this class).

 +id+:: is the ID of the transaction, an integer
 +date+:: is the date/time of the transaction
 +amount+:: is the amount, an instance of class +Amount+
 +prefix+:: is the prefix from the Invoice (read the WP)
 +bnf+:: is the wallet ID of the paying or receiving wallet
 +details+:: is the details, in plain text