docs: def get_agent_id(self):
          """Gets the ``Id`` of the ``Agent`` identified in this authentication credential.
  
          return: (osid.id.Id) - the ``Agent 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:
              return Id(identifier=self._django_user.get_username(),
                        namespace='osid.agent.Agent',
                        authority='MIT-OEIT')
          else:
              return Id(identifier='MC3GUE$T@MIT.EDU',
                        namespace='osid.agent.Agent',
                        authority='MIT-OEIT')