如何避免flask api出现CORS错误？

from flask import Flask
from flask_cors import CORS

app = Flask(__name__)
CORS(app)

@app.route('/api')
def api():
    return 'API response'

if __name__ == '__main__':
    app.run()

from flask import Flask

app = Flask(__name__)

@app.route('/api')
def api():
    response = make_response('API response')
    response.headers['Access-Control-Allow-Origin'] = '*'  # 允许所有域名访问
    response.headers['Access-Control-Allow-Methods'] = 'GET, POST, PUT, DELETE'  # 允许的HTTP方法
    response.headers['Access-Control-Allow-Headers'] = 'Content-Type'  # 允许的请求头
    return response

if __name__ == '__main__':
    app.run()

location /api {
    proxy_pass http://localhost:5000;  # 将请求转发给Flask应用
    add_header 'Access-Control-Allow-Origin' '*' always;  # 允许所有域名访问
    add_header 'Access-Control-Allow-Methods' 'GET, POST, PUT, DELETE' always;  # 允许的HTTP方法
    add_header 'Access-Control-Allow-Headers' 'Content-Type' always;  # 允许的请求头
}