Function await_signature_shares 

pub(crate) async fn await_signature_shares(
    db: &Database,
    range: OutPointRange,
) -> Vec<BlindedSignatureShare>

The signature shares of the range, waiting for them to be written. A transaction’s outputs are processed in one database transaction, so the range’s last share appearing means every share has, and the wait is on that one. An empty or descending range, which an untrusted request may carry, has no shares.