How to pass an argument to a spark submit job in airflow

I have to trigger a pyspark module from airflow using a sparksubmit operator. But, the pyspark module need to take the spark session variable as an argument. I have used application_args to pass the parameter to the pyspark module. But, when I ran the dag the spark submit operator is getting failed and the parameter I passed in considered as None type variable. Need to know how to pass a argument to a pyspark module triggered through spark_submit_operator.

The DAG code is below:

from pyspark.sql import SparkSession
spark = SparkSession.builder.appName("PRJT").enableHiveSupport().getOrCreate()

spark_config = {
    'conn_id': 'spark_default',
    'driver_memory': '1g',
    'executor_cores': 1,
    'num_executors': 1,
    'executor_memory': '1g'
}

dag = DAG(
    dag_id="spark_session_prgm",
    default_args=default_args,
    schedule_interval='@daily',
    catchup=False)

spark_submit_task1 = SparkSubmitOperator(
    task_id='spark_submit_task1',
    application='/home/airflow_home/dags/tmp_spark_1.py',
    application_args=['spark'],
    **spark_config, dag=dag)

The sample code in tmp_spark_1.py program: