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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def build_label(self, ident, cls):
 """ match nodes by a label """

        ident_w_label = ident + ':' + cls.__label__
        self._ast['match'].append('({0})'.format(ident_w_label))
        self._ast['return'] = ident
        self._ast['result_class'] = cls
        return ident