value = context['task_instance'].xcom_pull(task_ids='pushing_task')
sub_dag = SubDagOperator(subdag=sub_dag(PARENT_DAG_NAME, CHILD_DAG_NAME,
    main_dag.start_date, main_dag.schedule_interval, value), task_id=
    CHILD_DAG_NAME, dag=main_dag)
Proper way to create dynamic workflows in Airflow