def get_proficiency_notification_session(self, proficiency_receiver=None):
raise Unimplemented()<EOL>
Gets the OsidSession associated with the proficiency
        notification service.

        arg:    proficiencyReceiver (osid.learning.ProficiencyReceiver):
                the notification callback
        return: (osid.learning.ProficiencyNotificationSession) - a
                ProficiencyNotificationSession
        raise:  NullArgument - proficiencyReceiver is null
        raise:  OperationFailed - unable to complete request
        raise:  Unimplemented - supports_proficiency_notification() is
                false
        compliance: optional - This method must be implemented if
                    supports_proficiency_notification() is true.