def _proxy(self):
        """
        Generate an instance context for the instance, the context is capable of
        performing various actions.  All instance actions are proxied to the context

        :returns: ChallengeContext for this ChallengeInstance
        :rtype: twilio.rest.authy.v1.service.entity.factor.challenge.ChallengeContext
        """
        if self._context is None:
            self._context = ChallengeContext(
                self._version,
                service_sid=self._solution['service_sid'],
                identity=self._solution['identity'],
                factor_sid=self._solution['factor_sid'],
                sid=self._solution['sid'],
            )
        return self._context
Generate an instance context for the instance, the context is capable of
        performing various actions.  All instance actions are proxied to the context

        :returns: ChallengeContext for this ChallengeInstance
        :rtype: twilio.rest.authy.v1.service.entity.factor.challenge.ChallengeContext