def get_book_notification_session(self, book_receiver=None, proxy=None):
if proxy is None:<EOL><INDENT>raise NullArgument()<EOL><DEDENT>raise Unimplemented()<EOL>
Gets the ``OsidSession`` associated with the book notification service.

        arg:    book_receiver (osid.commenting.BookReceiver): the
                receiver
        arg:    proxy (osid.proxy.Proxy): a proxy
        return: (osid.commenting.BookNotificationSession) - a
                ``BookNotificationSession``
        raise:  NullArgument - ``book_receiver`` or ``proxy`` is
                ``null``
        raise:  OperationFailed - unable to complete request
        raise:  Unimplemented - ``supports_book_notification()`` is
                ``false``
        *compliance: optional -- This method must be implemented if
        ``supports_book_notification()`` is ``true``.*