invokes TouchWorksMagicConstants.ACTION_GET_ENCOUNTER_LIST_FOR_PATIENT action
        :return: JSON response

def get_patient_activity(self, patient_id, since=''):
        """
        invokes TouchWorksMagicConstants.ACTION_GET_ENCOUNTER_LIST_FOR_PATIENT action
        :return: JSON response
        """
        magic = self._magic_json(
            action=TouchWorksMagicConstants.ACTION_GET_PATIENT_ACTIVITY,
            patient_id=patient_id,
            parameter1=since)
        response = self._http_request(TouchWorksEndPoints.MAGIC_JSON, data=magic)
        result = self._get_results_or_raise_if_magic_invalid(
            magic,
            response,
            TouchWorksMagicConstants.RESULT_GET_PATIENT_ACTIVITY)
        return result