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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 flush(self):
 """Closes the underlying zip file, ensuring all records are written, then re-opens the file for further modifications."""

        if self.mode != 'r':
            with self.mutex:
                self.zf.close()
                # N.B., re-open with mode 'a' regardless of initial mode so we don't wipe
                # what's been written
                self.zf = zipfile.ZipFile(self.path, mode='a',
                                          compression=self.compression,
                                          allowZip64=self.allowZip64)