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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 fetch(self):
 """ Fetch a StepContextInstance :returns: Fetched StepContextInstance :rtype: twilio.rest.studio.v1.flow.engagement.step.step_context.StepContextInstance """

        params = values.of({})

        payload = self._version.fetch(
            'GET',
            self._uri,
            params=params,
        )

        return StepContextInstance(
            self._version,
            payload,
            flow_sid=self._solution['flow_sid'],
            engagement_sid=self._solution['engagement_sid'],
            step_sid=self._solution['step_sid'],
        )