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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 prepare_series(self) -> None: # noinspection PyUnresolvedReferences """Call |XMLSubseries.prepare_series| of all |XMLSubseries| objects with the same memory |set| object. True set() True """

        memory = set()
        for output in itertools.chain(self.readers, self.writers):
            output.prepare_series(memory)