how to check which submit button is clicked in flask wtf

from flask import Flask, render_template, request
from flask_wtf import FlaskForm
from wtforms import SubmitField

app = Flask(__name__)
app.config['SECRET_KEY'] = 'your_secret_key'

class MyForm(FlaskForm):
    submit_button_1 = SubmitField('Submit Button 1')
    submit_button_2 = SubmitField('Submit Button 2')

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

    if form.validate_on_submit():
        if form.submit_button_1.data:
            return 'Submit Button 1 clicked'
        elif form.submit_button_2.data:
            return 'Submit Button 2 clicked'

    return render_template('index.html', form=form)

if __name__ == '__main__':
    app.run(debug=True)
<!-- templates/index.html -->
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Flask WTF - Submit Button</title>
</head>
<body>
    <form method="post" action="/">
        {{ form.hidden_tag() }}
        {{ form.submit_button_1 }}
        {{ form.submit_button_2 }}
    </form>
</body>
</html>