Function verify_expected_acknowledgements 

pub fn verify_expected_acknowledgements<V>(
    peer: OffchainPublicKey,
    acks: Vec<Acknowledgement>,
    awaiting_acks: &Cache<OffchainPublicKey, V>,
    use_batch_verification: bool,
) -> Option<(V, Vec<(HalfKey, HalfKeyChallenge)>)>
where
    V: Clone + Send + Sync + 'static,

Checks whether an acknowledgement from peer is currently expected (by looking at the awaiting_acks cache) and, if so, verifies all incoming acks.

The lookup is performed in two steps so that the popularity estimator of the peer entry inside awaiting_acks is not bumped on the initial existence check, allowing the entry to time out naturally on inactivity.

When use_batch_verification is true, [Acknowledgement::verify_batch] is used, which transparently falls back to per-acknowledgement verification for small batches and switches to the more effective batch verification algorithm for larger ones. Otherwise, each acknowledgement is verified individually.

Returns the cloned per-peer cache entry alongside the verified (half-key, challenge) pairs, or None if no acknowledgement is expected from peer. Invalid acknowledgements are logged and silently dropped.