pub trait Body {
// Required methods
fn poll_chunk(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &mut [u8],
) -> Poll<Result<usize>>;
fn poll_chunk_size_hint(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<Result<(usize, Option<usize>)>>;
fn size_hint(&self) -> (usize, Option<usize>);
}