@abc.abstractmethod<EOL><INDENT>def get_book_search_order(self):<DEDENT>
return<EOL>
Gets a book search order.

        The ``BookSearchOrder`` is supplied to a ``BookSearch`` to
        specify the ordering of results.

        :return: the book search order
        :rtype: ``osid.commenting.BookSearchOrder``


        *compliance: mandatory -- This method must be implemented.*