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: lib.rs
    path of file: ./repos/ntex/ntex-rt/src
    
    the code of the file until where you have to start completion: //! A runtime implementation that runs everything on the current thread.
use std::{cell::RefCell, ptr};

mod arbiter;
mod builder;
mod system;

pub use self::arbiter::Arbiter;
pub use self:
    
        fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
            match self.fut {
                Either::Left(ref mut f) => match Pin::new(f).poll(cx) {
                    Poll::Pending => Poll::Pending,
                    Poll::Ready(res) => Poll::Ready(res.ok_or(Canceled)),
                },
                Either::Right(ref mut f) => Pin::new(f).poll(cx),
            }
        }