千问这个web_demo的API怎么调用？

[running-frog]

from gradio_client import Client

client = Client("http://127.0.0.1:7860/")
result = client.predict(
"Howdy!", # str in 'Input' Textbox component
"null", # str (filepath to JSON file) in 'Qwen-7B-Chat' Chatbot component
fn_index=0
)
print(result)

这里面的“null”指的是哪个文件？