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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 extract_means_or_values(cls, observation, prediction, key=None):
 """Extracts the mean, value, or user-provided key from the observation and prediction dictionaries. """


        obs_mv = cls.extract_mean_or_value(observation, key)
        pred_mv = cls.extract_mean_or_value(prediction, key)
        return obs_mv, pred_mv