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: flag.rs
    path of file: ./repos/s2n-quic/quic/s2n-quic-transport/src/sync
    
    the code of the file until where you have to start completion: // Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0

//! Sends a "flag" frame towards the peer
//!
//! This is intended to be used by frames, like PING and HANDSHAKE_DONE, that don't have any
//! content other than the frame
    
    pub fn on_packet_ack<A: ack::Set>(&mut self, ack_set: &A) -> bool {
        if let DeliveryState::InFlight { stable, latest } = &self.delivery {
            if ack_set.contains(*stable) || ack_set.contains(*latest) {
                self.finish();
                return true;
            }
        }

        false
    }