def annotate_timetable(timetable, *annotate_funcs):
    """Annotates all entries of *timetable* with the result of all
    *annotate_funcs*. The annotation functions must accept the arguments
    *start*, *end*, *entry*.
    """
    for start, end, entry in timetable:
        for annotate_func in annotate_funcs:
            annotate_func(start, end, entry)
        yield start, end, entry
