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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_max_drift_csig(self):
 """ Returns the content signature currently stored for this node if it's been unmodified longer than the max_drift value, or the max_drift value is 0. Returns None otherwise. """

        old = self.get_stored_info()
        mtime = self.get_timestamp()

        max_drift = self.fs.max_drift
        if max_drift > 0:
            if (time.time() - mtime) > max_drift:
                try:
                    n = old.ninfo
                    if n.timestamp and n.csig and n.timestamp == mtime:
                        return n.csig
                except AttributeError:
                    pass
        elif max_drift == 0:
            try:
                return old.ninfo.csig
            except AttributeError:
                pass

        return None