@Override
  protected int compareByFee(final PendingTransaction pt1, final PendingTransaction pt2) {
    return comparing(PendingTransaction::getScore)
        .thenComparing(PendingTransaction::hasPriority)
        .thenComparing(PendingTransaction::getGasPrice)
        .thenComparing(PendingTransaction::getSequence)
        .compare(pt1, pt2);
  }
Holds the current set of pending transactions with the ability to iterate them based on priority
for mining or look-up by hash.

<p>This class is safe for use across multiple threads.
ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/transactions/layered/GasPricePrioritizedTransactions.java