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