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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 selfsig(self):
 """ This will be the most recent, self-signature of this User ID or Attribute. If there isn't one, this will be ``None``. """

        if self.parent is not None:
            return next((sig for sig in reversed(self._signatures) if sig.signer == self.parent.fingerprint.keyid), None)