我们如何处理Flask中的空表单？

@app.route('/submit', methods=['POST'])
def submit_form():
    # 处理表单提交的逻辑
    pass

from flask import request

@app.route('/submit', methods=['POST'])
def submit_form():
    if len(request.form) == 0:
        # 处理空表单的逻辑
        pass
    else:
        # 处理非空表单的逻辑
        pass

from flask import render_template

@app.route('/submit', methods=['POST'])
def submit_form():
    if len(request.form) == 0:
        error_message = '表单不能为空'
        return render_template('form.html', error=error_message)
    else:
        # 处理非空表单的逻辑
        pass