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"""Example DAG demonstrating the usage of the @taskgroup decorator."""
from __future__ import annotations

import pendulum

from airflow.decorators import task, task_group
from airflow.models.dag import DAG


# [START howto_task_group_decorator]
# Creating Tasks
@task
def task_start():
    """Empty Task which is First Task of Dag"""
    return '[Task_start]'


@task
def task_1(value: int) -> str:
    """Empty Task1"""
    return f'[ Task1 {value} ]'


@task
def task_2(value: str) -> str:
    """Empty Task2"""
    return f'[ Task2 {value} ]'


@task
def task_3(value: str) -> None:
    """Empty Task3"""
    print(f'[ Task3 {value} ]')


@task
def task_end() -> None:
    """Empty Task which is Last Task of Dag"""
    print('[ Task_End  ]')


# Creating TaskGroups
@task_group
def task_group_function(value: int) -> None:
    """TaskGroup for grouping related Tasks"""
    task_3(task_2(task_1(value)))


# Executing Tasks and TaskGroups
with DAG(
    dag_id="example_task_group_decorator",
    start_date=pendulum.datetime(2021, 1, 1, tz="UTC"),
    catchup=False,
    tags=["example"],
) as dag:
    start_task = task_start()
    end_task = task_end()
    for i in range(5):
        current_task_group = task_group_function(i)
        start_task >> current_task_group >> end_task

# [END howto_task_group_decorator]
