Google Cloud Dataproc cluster creation failure due to Cloud SQL proxy initialization error

I am trying to create a Dataproc cluster from a Cloud Composer DAG using the DataprocCreateClusterOperator of Airflow. I need to access Cloud SQL from my Dataproc cluster hence need to install the Cloud SQL proxy on the cluster as well. I am providing the initialization action for Cloud SQL Proxy as per docs in my cluster config for the Airflow operator as below:

"initialization_actions": [
        {
           "executable_file" : "gs://<<some_gcs_bucket>>/cloud-sql-proxy.sh"
        }
    ],

"gce_cluster_config": {
        "service_account_scopes": ["https://www.googleapis.com/auth/cloud-platform","https://www.googleapis.com/auth/sqlservice.admin"],
        "metadata" : {
             "enable-cloud-sql-hive-metastore" : "false",
             "additional-cloud-sql-instances" : "<<PROJECT_ID>>:<<REGION>>:<<INSTANCE_NAME>>"
        }
    }

The cluster creation fails with below message:

google.api_core.exceptions.InvalidArgument: 400 Initialization action failed. Failed action 'gs://<<some_gcs_bucket>>/cloud-sql-proxy.sh', see output in: gs://<<some_gcs_bucket>>/dataproc-initialization-script-0_output

I might be putting the parameters in the cluster config wrongly like the metadata arguments required by the initialization script, if anybody has implemented this use-case previously then would appreciate your inputs.