这段程序会输出什么？

def application(environ, start_response):
    start_response("200 OK", [])
    yield b"A"
    yield b"B"

statuses = []

def start_response(status, headers, exc_info=None):
    statuses.append(status)
    return lambda data: None

result = application({}, start_response)
print(statuses)
print(list(result))
print(statuses)