How to use the flexmock.InvalidMethodSignature function in flexmock

elif expectation.return_values:
          return_value = expectation.return_values[0]
          expectation.return_values = expectation.return_values[1:]
          expectation.return_values.append(return_value)
        else:
          return_value = ReturnValue()
        if return_value.raises:
          if inspect.isclass(return_value.raises):
            raise return_value.raises(
                *return_value.value['kargs'], **return_value.value['kwargs'])
          else:
            raise return_value.raises
        else:
          return return_value.value
      else:
        raise InvalidMethodSignature(_format_args(method, arguments))
    return mock_method

def pass_thru(expectation, *kargs, **kwargs):
      return_values = None
      try:
        return_values = expectation.original_method(*kargs, **kwargs)
      except:
        return _handle_exception_matching(expectation)
      if (expectation.return_values and
          not match_return_values(expectation.return_values[0].value,
                                  return_values)):
        raise (InvalidMethodSignature('expected to return %s, returned %s' %
               (expectation.return_values[0], return_values)))
      return return_values