You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: flatten.rs
    path of file: ./repos/phaser/phaser/vendor/futures-util/src/future/future
    
    the code of the file until where you have to start completion: use core::pin::Pin;
use futures_core::future::{FusedFuture, Future};
use futures_core::ready;
use futures_core::stream::{FusedStream, Stream};
use futures_core::task::{Context, Poll};
#[cfg(feature = "sink")]
use futures_sink::Sink;
use pin_project_lite::pin_project;

pin_project! {
   
    
    fn poll_close(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
        let res = match self.as_mut().project() {
            FlattenProj::Second { f } => f.poll_close(cx),
            _ => Poll::Ready(Ok(())),
        };
        if res.is_ready() {
            self.set(Self::Empty);
        }
        res
    }