code: def update(self, fallback_actions=values.unset):
          
          data = values.of({'FallbackActions': serialize.object(fallback_actions), })
  
          payload = self._version.update(
              'POST',
              self._uri,
              data=data,
          )
  
          return AssistantFallbackActionsInstance(
              self._version,
              payload,
              assistant_sid=self._solution['assistant_sid'],
          )
docs: Update the AssistantFallbackActionsInstance
  
          :param dict fallback_actions: The fallback_actions
  
          :returns: Updated AssistantFallbackActionsInstance
          :rtype: twilio.rest.preview.understand.assistant.assistant_fallback_actions.AssistantFallbackActionsInstance