code: def clear_state(self, activity, agent, registration=None):
          
          return self._delete_state(
              activity=activity,
              agent=agent,
              registration=registration
          )
docs: Clear state(s) with specified activity and agent
  
          :param activity: Activity object of state(s) to be deleted
          :type activity: :class:`tincan.activity.Activity`
          :param agent: Agent object of state(s) to be deleted
          :type agent: :class:`tincan.agent.Agent`
          :param registration: registration UUID of state(s) to be deleted
          :type registration: str | unicode
          :return: LRS Response object
          :rtype: :class:`tincan.lrs_response.LRSResponse`