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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 _flat_values(self):
 """Return tuple of mean values as found in cube response. Mean data may include missing items represented by a dict like {'?': -1} in the cube response. These are replaced by np.nan in the returned value. """

        return tuple(
            np.nan if type(x) is dict else x
            for x in self._cube_dict["result"]["measures"]["mean"]["data"]
        )