<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def rollback(self, date):
 """Roll date backward to nearest end of quarter"""

        if self.onOffset(date):
            return date
        else:
            return date - QuarterEnd(month=self.month)