def custom_cmp_end_time(self, x, y):
    if (x.end_time < y.end_time):
        return (- 1)
    elif (x.end_time > y.end_time):
        return 1
    else:
        return 0
def custom_cmp_end_time(self, x, y):
    if (x.end_time < y.end_time):
        return (- 1)
    elif (x.end_time > y.end_time):
        return 1
    else:
        return 0