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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):
 """ Writes current changes to disk and flushes modified objects in the AAFObjectManager """

        if self.mode in ("wb+", 'rb+'):
            if not self.is_open:
                raise IOError("file closed")
            self.write_reference_properties()
            self.manager.write_objects()