<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def check_schedule():
 """Helper routine to easily test if the schedule is valid"""

    all_items = prefetch_schedule_items()
    for validator, _type, _msg in SCHEDULE_ITEM_VALIDATORS:
        if validator(all_items):
            return False

    all_slots = prefetch_slots()
    for validator, _type, _msg in SLOT_VALIDATORS:
        if validator(all_slots):
            return False
    return True