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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 update(self, friendly_name=values.unset):
 """ Update the SigningKeyInstance :param unicode friendly_name: The friendly_name :returns: Updated SigningKeyInstance :rtype: twilio.rest.api.v2010.account.signing_key.SigningKeyInstance """

        data = values.of({'FriendlyName': friendly_name, })

        payload = self._version.update(
            'POST',
            self._uri,
            data=data,
        )

        return SigningKeyInstance(
            self._version,
            payload,
            account_sid=self._solution['account_sid'],
            sid=self._solution['sid'],
        )