How to use the croniter.croniter.croniter function in croniter

def update_next_trigger_at(self):
        tz = pytz.timezone(self.timezone)
        dt = tz.normalize(django_timezone.now())
        self.next_trigger_at = croniter(self.schedule, dt).get_next(datetime)

def update_next_trigger_at(self):
        base_time = django_timezone.now().replace(tzinfo=pytz.timezone(self.timezone))
        self.next_trigger_at = croniter(self.schedule, base_time).get_next(datetime)

def _update_next_trigger_at(self):
        """
        Defines next backup creation time
        """
        base_time = django_timezone.now().replace(tzinfo=pytz.timezone(self.timezone))
        self.next_trigger_at = croniter(self.schedule, base_time).get_next(datetime)

def initialize(self):
        """Initialize croniter and related times"""
        if self.croniter is None:
            self.time = time.time()
            self.datetime = datetime.now(get_localzone())
            self.loop_time = self.loop.time()
            self.croniter = croniter(self.spec, start_time=self.datetime)

def get_next_utc_execution(self):
        tz = pytz.timezone(self.timezone)

        if not self.next_execution:
            base = tz.normalize(datetime.now(tz) - timedelta(minutes=1))
        elif self.skip_delayed_jobs_next_time:
            base = tz.normalize(datetime.now(tz))
        else:
            base = tz.normalize(self.next_execution.replace(tzinfo=pytz.utc))

        cron = croniter(self.schedule, base)

        return cron.get_next(datetime).astimezone(pytz.utc)