def get_parent_book_nodes(self):
parent_book_nodes = []<EOL>for node in self._my_map['<STR_LIT>']:<EOL><INDENT>parent_book_nodes.append(BookNode(<EOL>node._my_map,<EOL>runtime=self._runtime,<EOL>proxy=self._proxy,<EOL>lookup_session=self._lookup_session))<EOL><DEDENT>return BookNodeList(parent_book_nodes)<EOL>
Gets the parents of this book.

        return: (osid.commenting.BookNodeList) - the parents of this
                book
        *compliance: mandatory -- This method must be implemented.*