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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 save(self):
 """ Update the SouceReading information for the currently recorded observations and then flush those to a file. @return: mpc_filename of the resulting save. """

        self.get_writer().flush()
        mpc_filename = self.get_writer().get_filename()
        self.get_writer().close()
        self._writer = None
        return mpc_filename