@abc.abstractmethod<EOL><INDENT>def get_comment_ids_by_book(self, book_id):<DEDENT>
return<EOL>
Gets the list of Comment Ids associated with a ``Book``.

        :param book_id: ``Id`` of a ``Book``.
        :type book_id: ``osid.id.Id``
        :return: list of related comment ``Ids``
        :rtype: ``osid.id.IdList``
        :raise: ``NotFound`` -- ``book_id`` is not found
        :raise: ``NullArgument`` -- ``book_id`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

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