docs: def get_agent_id(self):
          """Gets the ``Id`` of the ``Agent`` identified in this authentication credential.
  
          :return: the ``Agent Id``
          :rtype: ``osid.id.Id``
  
          *compliance: mandatory -- This method must be implemented.*
          *implementation notes*: The Agent should be determined at the
          time this credential is created.
  
          """
          if self._django_user is not None:
              if self._use_user_id:
                  identifier = self._django_user.id
              else:
                  identifier = self._django_user.get_username()
              return Id(identifier=identifier,
                        namespace='osid.agent.Agent',
                        authority='MIT-ODL')
          else:
              # perhaps this id should come from django settings?
              return Id(identifier='MC3GUE$T@MIT.EDU',
                        namespace='osid.agent.Agent',
                        authority='MIT-ODL')