celery create periodic tasks in different ways

tasks.py

from celery.task import periodic_task
from datetime import timedelta

# first way
@periodic_task(run_every=timedelta(seconds=10), exchange="default", routing_key="default")
def every_10_seconds():
    print("This is test")
    return 1
    

# second way
from celery.task import PeriodicTask
class MyPeriodTask(PeriodicTask):
    run_every = timedelta(seconds=6)
    options = {"exchange": "default", "routing_key": "default"}
    name = "xxxxx"

    def run(self):
        print("this is test")
        return 2


# 3th way
def run_period_task():
    """
        this way must define CELERYBEAT_SCHEDULE in config file like:
        CELERYBEAT_SCHEDULE = {
            'run_period_task': {
                'task': '<project>.tasks.run_period_task',
                'schedule': timedelta(seconds=30)
            },
        }
        # http://celery.readthedocs.io/en/latest/userguide/periodic-tasks.html
    """
    print("this is test")
    return 3