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"""
Example LatestOnlyOperator and TriggerRule interactions
"""
from __future__ import annotations

# [START example]
import datetime

import pendulum

from airflow import DAG
from airflow.operators.empty import EmptyOperator
from airflow.operators.latest_only import LatestOnlyOperator
from airflow.utils.trigger_rule import TriggerRule

with DAG(
    dag_id='latest_only_with_trigger',
    schedule=datetime.timedelta(hours=4),
    start_date=pendulum.datetime(2021, 1, 1, tz="UTC"),
    catchup=False,
    tags=['example3'],
) as dag:
    latest_only = LatestOnlyOperator(task_id='latest_only')
    task1 = EmptyOperator(task_id='task1')
    task2 = EmptyOperator(task_id='task2')
    task3 = EmptyOperator(task_id='task3')
    task4 = EmptyOperator(task_id='task4', trigger_rule=TriggerRule.ALL_DONE)

    latest_only >> task1 >> [task3, task4]
    task2 >> [task3, task4]
# [END example]
