def get_agent_notification_session(self, agent_receiver=None, proxy=None):
if proxy is None:<EOL><INDENT>raise NullArgument()<EOL><DEDENT>raise Unimplemented()<EOL>
Gets the messaging receiver session for notifications pertaining to agent changes.

        arg:    agent_receiver (osid.authentication.AgentReceiver): the
                agent receiver
        arg:    proxy (osid.proxy.Proxy): a proxy
        return: (osid.authentication.AgentNotificationSession) - an
                ``AgentNotificationSession``
        raise:  NullArgument - ``proxy`` or ``agent_receiver`` is null
        raise:  OperationFailed - unable to complete request
        raise:  Unimplemented - ``supports_agent_notification()`` is
                ``false``
        *compliance: optional -- This method must be implemented if
        ``supports_agent_notification()`` is ``true``.*