returned the entire page (including < html >)

I have tried everything that I feel I can search for

app.locals.layout=false
res.locals.layout=false
res.render({layout: false})

there are two other things that you can"t remember clearly view option

returns the whole page all the time
the file is layout.pug , index.pug , index inherits layout.pug

the question is how to avoid using layout on a single page in a Pug+express4 environment