def get_composition_notification_session(self, composition_receiver=None):
if composition_receiver is None:<EOL><INDENT>raise NullArgument()<EOL><DEDENT>if not self.supports_composition_notification():<EOL><INDENT>raise Unimplemented()<EOL><DEDENT>try:<EOL><INDENT>from . import sessions<EOL><DEDENT>except ImportError:<EOL><INDENT>raise  <EOL><DEDENT>try:<EOL><INDENT>session = sessions.CompositionNotificationSession(composition_receiver,<EOL>proxy=self._proxy,<EOL>runtime=self._runtime)<EOL><DEDENT>except AttributeError:<EOL><INDENT>raise  <EOL><DEDENT>return session<EOL>
Gets the notification session for notifications pertaining to
        composition changes.

        arg:    composition_receiver
                (osid.repository.CompositionReceiver): the notification
                callback
        return: (osid.repository.CompositionNotificationSession) - a
                CompositionNotificationSession
        raise:  NullArgument - composition_receiver is null
        raise:  OperationFailed - unable to complete request
        raise:  Unimplemented - supports_composition_notification() is
                false
        compliance: optional - This method must be implemented if
                    supports_composition_notification() is true.