Given this WSGI middleware code wrapping a Flask app, what will be printed when a request is made?

Given this WSGI middleware code wrapping a Flask app, what will be printed when a request is made?

class SimpleMiddleware:
    def __init__(self, app):
        self.app = app
    def __call__(self, environ, start_response):
        print('Before app')
        response = self.app(environ, start_response)
        print('After app')
        return response

app = Flask(__name__)
app = SimpleMiddleware(app)