vim.fn is nil

[pistacio520]

Hello! I watched vim-fundamentals video ,
I want to do lua script (about use lua script to sort quickfix list )but my lua chunk can't run,
Then I type command : lua print(vim.fn) ,return a nil value
is it I ｄｏｎ＇ｔ ｉｎｓｔａｌｌ ｖｉｍ－ｌｕａ ｍｏｄｕｌｅ？