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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 __read_stored_routine_metadata(self):
 """ Reads the metadata of stored routines from the metadata file. """

        if os.path.isfile(self._pystratum_metadata_filename):
            with open(self._pystratum_metadata_filename, 'r') as file:
                self._pystratum_metadata = json.load(file)