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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 _get_mark_if_any(self):
 """Parse a mark section."""

        line = self.next_line()
        if line.startswith(b'mark :'):
            return line[len(b'mark :'):]
        else:
            self.push_line(line)
            return None