@Override
  protected TransactionAddedResult canAdd(
      final PendingTransaction pendingTransaction, final int gap) {
    gapBySender.compute(
        pendingTransaction.getSender(),
        (sender, currGap) -> {
          if (currGap == null) {
            orderByGap.get(gap).add(pendingTransaction);
            return gap;
          }
          if (Long.compareUnsigned(
                  pendingTransaction.getNonce(), txsBySender.get(sender).firstKey())
              < 0) {
            orderByGap.get(currGap).remove(sender);
            orderByGap.get(gap).add(pendingTransaction);
            return gap;
          }
          return currGap;
        });

    return TransactionAddedResult.ADDED;
  }
Order sparse tx by priority flag and sequence asc, so that we pick for eviction txs that have
no priority and with the lowest sequence number (oldest) first.
ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/transactions/layered/SparseTransactions.java