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: acknowledged_message.rs
    path of file: ./repos/mongo-rust-driver/src/runtime
    
    the code of the file until where you have to start completion: use std::{pin::Pin, task::Poll};

use futures_core::Future;

/// A message type that includes an acknowledgement mechanism.
/// When this is dropped or `acknowledge` is called, the sender will be notified.
#[derive(Debug)]
pub(crate) struct AcknowledgedMessage
    
    pub(crate) fn package(message: M) -> (Self, AcknowledgmentReceiver<R>) {
        let (sender, receiver) = tokio::sync::oneshot::channel();
        (
            Self {
                message,
                acknowledger: AcknowledgmentSender { sender },
            },
            AcknowledgmentReceiver { receiver },
        )
    }