How to document the post body using flask-ReSTplus?

I have solved it (partially) using the following model

""" Model for documenting the API"""

insert_user_data = ns_database.model(
    "Insert_user_data",
    {
        "customer_id": fields.String(description="cust ID", required=True),
        "service_id": fields.String(description="service ID", required=True),
        "customer_name": fields.String(description="Customer1", required=True),
        "site_name": fields.String(description="site", required=True),
        "service_type": fields.String(description="service", required=True),
    },
)


@ns_database.route("/insert_user")
class database(Resource):
    @ns_database.expect(insert_user_data)
    def post(self):
        """insert data"""
        json_data = request.json
        customer_id = json_data["customer_id"]
        service_id = json_data["service_id"]
        customer_name = json_data["customer_name"]
        site_name = json_data["site_name"]
        service_type = json_data["service_type"]

now the API shows model for data input and an example