How to use the apscheduler.util.astimezone function in APScheduler

def test_str(self):
        value = astimezone('Europe/Helsinki')
        assert isinstance(value, tzinfo)

def test_tz(self):
        tz = pytz.timezone('Europe/Helsinki')
        value = astimezone(tz)
        assert tz is value

def __init__(self, weeks=0, days=0, hours=0, minutes=0, seconds=0, start_date=None, end_date=None, timezone=None):
        self.interval = timedelta(weeks=weeks, days=days, hours=hours, minutes=minutes, seconds=seconds)
        self.interval_length = timedelta_seconds(self.interval)
        if self.interval_length == 0:
            self.interval = timedelta(seconds=1)
            self.interval_length = 1

        if timezone:
            self.timezone = astimezone(timezone)
        elif start_date and start_date.tzinfo:
            self.timezone = start_date.tzinfo
        elif end_date and end_date.tzinfo:
            self.timezone = end_date.tzinfo
        else:
            self.timezone = get_localzone()

        start_date = start_date or (datetime.now(self.timezone) + self.interval)
        self.start_date = convert_to_datetime(start_date, self.timezone, 'start_date')
        self.end_date = convert_to_datetime(end_date, self.timezone, 'end_date')

def _add_job_to_scheduler(self, trigger):
        trigger_type_ref = trigger['type']
        trigger_type = TIMER_TRIGGER_TYPES[trigger_type_ref]
        try:
            jsonschema.validate(trigger['parameters'],
                                trigger_type['parameters_schema'])
        except jsonschema.ValidationError as e:
            LOG.error('Exception scheduling timer: %s, %s',
                      trigger['parameters'], e, exc_info=True)
            raise  # Or should we just return?

        time_spec = trigger['parameters']
        time_zone = aps_utils.astimezone(trigger['parameters'].get('timezone'))

        time_type = None

        if trigger_type['name'] == 'st2.IntervalTimer':
            unit = time_spec.get('unit', None)
            value = time_spec.get('delta', None)
            time_type = IntervalTrigger(**{unit: value, 'timezone': time_zone})
        elif trigger_type['name'] == 'st2.DateTimer':
            # Raises an exception if date string isn't a valid one.
            dat = date_parser.parse(time_spec.get('date', None))
            time_type = DateTrigger(dat, timezone=time_zone)
        elif trigger_type['name'] == 'st2.CronTimer':
            cron = time_spec.copy()
            cron['timezone'] = time_zone

            time_type = CronTrigger(**cron)

def __init__(self, year=None, month=None, day=None, week=None, day_of_week=None, hour=None,
                 minute=None, second=None, start_date=None, end_date=None, timezone=None,
                 jitter=None):
        if timezone:
            self.timezone = astimezone(timezone)
        elif isinstance(start_date, datetime) and start_date.tzinfo:
            self.timezone = start_date.tzinfo
        elif isinstance(end_date, datetime) and end_date.tzinfo:
            self.timezone = end_date.tzinfo
        else:
            self.timezone = get_localzone()

        self.start_date = convert_to_datetime(start_date, self.timezone, 'start_date')
        self.end_date = convert_to_datetime(end_date, self.timezone, 'end_date')

        self.jitter = jitter

        values = dict((key, value) for (key, value) in locals().items()
                      if key in self.FIELD_NAMES and value is not None)
        self.fields = []
        assign_defaults = False

trigger_type_ref = trigger['type']
        trigger_type = TIMER_TRIGGER_TYPES[trigger_type_ref]
        try:
            util_schema.validate(
                instance=trigger['parameters'],
                schema=trigger_type['parameters_schema'],
                cls=util_schema.CustomValidator,
                use_default=True,
                allow_default_none=True,
            )
        except jsonschema.ValidationError as e:
            LOG.error('Exception scheduling timer: %s, %s', trigger['parameters'], e, exc_info=True)
            raise  # Or should we just return?

        time_spec = trigger['parameters']
        time_zone = aps_utils.astimezone(trigger['parameters'].get('timezone'))

        time_type = None

        if trigger_type['name'] == 'st2.IntervalTimer':
            unit = time_spec.get('unit', None)
            value = time_spec.get('delta', None)
            time_type = IntervalTrigger(**{unit: value, 'timezone': time_zone})
        elif trigger_type['name'] == 'st2.DateTimer':
            # Raises an exception if date string isn't a valid one.
            dat = date_parser.parse(time_spec.get('date', None))
            time_type = DateTrigger(dat, timezone=time_zone)
        elif trigger_type['name'] == 'st2.CronTimer':
            cron = time_spec.copy()
            cron['timezone'] = time_zone

            time_type = CronTrigger(**cron)

def __init__(self, year=None, month=None, day=None, week=None, day_of_week=None, hour=None, minute=None,
                 second=None, start_date=None, end_date=None, timezone=None):
        if timezone:
            self.timezone = astimezone(timezone)
        elif start_date and start_date.tzinfo:
            self.timezone = start_date.tzinfo
        elif end_date and end_date.tzinfo:
            self.timezone = end_date.tzinfo
        else:
            self.timezone = get_localzone()

        self.start_date = convert_to_datetime(start_date, self.timezone, 'start_date')
        self.end_date = convert_to_datetime(end_date, self.timezone, 'end_date')

        values = dict((key, value) for (key, value) in six.iteritems(locals())
                      if key in self.FIELD_NAMES and value is not None)
        self.fields = []
        assign_defaults = False
        for field_name in self.FIELD_NAMES:
            if field_name in values:

def _configure(self, config):
        # Set general options
        self._logger = maybe_ref(config.pop('logger', None)) or getLogger('apscheduler.scheduler')
        self.timezone = astimezone(config.pop('timezone', None)) or get_localzone()
        self.jobstore_retry_interval = float(config.pop('jobstore_retry_interval', 10))

        # Set the job defaults
        job_defaults = config.get('job_defaults', {})
        self._job_defaults = {
            'misfire_grace_time': asint(job_defaults.get('misfire_grace_time', 1)),
            'coalesce': asbool(job_defaults.get('coalesce', True)),
            'max_instances': asint(job_defaults.get('max_instances', 1))
        }

        # Configure executors
        self._executors.clear()
        for alias, value in config.get('executors', {}).items():
            if isinstance(value, BaseExecutor):
                self.add_executor(value, alias)
            elif isinstance(value, MutableMapping):