<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def next_weekday(weekday):
 """Returns the name of the weekday after the given weekday name."""

    ix = WEEKDAYS.index(weekday)
    if ix == len(WEEKDAYS)-1:
        return WEEKDAYS[0]
    return WEEKDAYS[ix+1]