code: def get(self, sid):
          
          return AvailableAddOnExtensionContext(
              self._version,
              available_add_on_sid=self._solution['available_add_on_sid'],
              sid=sid,
          )
docs: Constructs a AvailableAddOnExtensionContext
  
          :param sid: The unique Extension Sid
  
          :returns: twilio.rest.preview.marketplace.available_add_on.available_add_on_extension.AvailableAddOnExtensionContext
          :rtype: twilio.rest.preview.marketplace.available_add_on.available_add_on_extension.AvailableAddOnExtensionContext