def __init__(self, cohort, start_day, end_day):
        self.cohort = cohort
        self.start_day = start_day
        self.end_day = end_day
        if 1 < self.start_day:
            raise ValueError("start day '%s' must be >= 1" % self.start_day)
        if self.start_day >= self.end_day:
            raise ValueError("start day '%s' must be before end day '%s'" %
                             (self.start_day, self.end_day))
        self._activities = None
        self._users = None
dataset/ETHPy150Open MontmereLimited/django-lean/django_lean/lean_retention/reports.py/Period.__init__/swapped operands of `<`