@utilities.arguments_not_none<EOL><INDENT>def get_child_books(self, book_id):<DEDENT>
<EOL>if self._catalog_session is not None:<EOL><INDENT>return self._catalog_session.get_child_catalogs(catalog_id=book_id)<EOL><DEDENT>return BookLookupSession(<EOL>self._proxy,<EOL>self._runtime).get_books_by_ids(<EOL>list(self.get_child_book_ids(book_id)))<EOL>
Gets the child books of the given ``id``.

        arg:    book_id (osid.id.Id): the ``Id`` of the ``Book`` to
                query
        return: (osid.commenting.BookList) - the child books of the
                ``id``
        raise:  NotFound - a ``Book`` identified by ``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.*