A string of the bar and space weights of the barcode. Starting with a bar and alternating.

        >>> barcode = Code128("Hello!", charset='B')
        >>> barcode.bars
        '2112142311131122142211142211141341112221221212412331112'

        :rtype: string

def bars(self):
        """A string of the bar and space weights of the barcode. Starting with a bar and alternating.

        >>> barcode = Code128("Hello!", charset='B')
        >>> barcode.bars
        '2112142311131122142211142211141341112221221212412331112'

        :rtype: string
        """
        return ''.join(map((lambda val: self._val2bars[val]), self.symbol_values))