code: def _proxy(self):
          
          if self._context is None:
              self._context = AvailableAddOnExtensionContext(
                  self._version,
                  available_add_on_sid=self._solution['available_add_on_sid'],
                  sid=self._solution['sid'],
              )
          return self._context
docs: Generate an instance context for the instance, the context is capable of
          performing various actions.  All instance actions are proxied to the context
  
          :returns: AvailableAddOnExtensionContext for this AvailableAddOnExtensionInstance
          :rtype: twilio.rest.preview.marketplace.available_add_on.available_add_on_extension.AvailableAddOnExtensionContext