def get_books_for_schedule(self, schedule):
        """
        Returns a dictionary of data.  SLNs are the keys, an array of Book
        objects are the values.
        """
        slns = self._get_slns(schedule)

        books = {}

        for sln in slns:
            try:
                section_books = self.get_books_by_quarter_sln(
                    schedule.term.quarter, sln
                )
                books[sln] = section_books
            except DataFailureException:
                # do nothing if bookstore doesn't have sln
                pass
        return books
Returns a dictionary of data.  SLNs are the keys, an array of Book
        objects are the values.