AJAX POST data does not show up in Python

    jQuery.post({
        url: "/getData",
        data: data,
        success: function (response) {
            alert("success");
            console.log(response);
        },
        dataType: "json",
        contentType: 'application/json'
    });

from flask import Flask, request, render_template_string, jsonify

app = Flask(__name__)

@app.route('/', methods=['GET', 'POST'])
def index():
    return render_template_string('''









''')

@app.route('/getData', methods=['GET', 'POST'])
def get_data():
    print('args :', request.args)
    print('form :', request.form)
    print('data :', request.data)
    print('json :', request.json)
    print('files:', request.files)
    return jsonify(["Hello World"])

if __name__ == '__main__':
    #app.debug = True 
    app.run()  

args : ImmutableMultiDict([])
form : ImmutableMultiDict([])
data : b'{"test_id":"1"}'
json : {'test_id': '1'}
files: ImmutableMultiDict([])