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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 _expected_argument_string(self):
 """Generates a string describing what arguments the double expected. :return: A string describing expected arguments. :rtype: str """


        if self.args is _any and self.kwargs is _any:
            return 'any args'
        elif self._custom_matcher:
            return "custom matcher: '{}'".format(self._custom_matcher.__name__)
        else:
            return build_argument_repr_string(self.args, self.kwargs)