@Override
  public void notifyAdded(final PendingTransaction pendingTransaction) {
    final Address sender = pendingTransaction.getSender();
    final var senderTxs = txsBySender.get(sender);
    if (senderTxs != null) {
      if (senderTxs.firstKey() < pendingTransaction.getNonce()) {
        // in the case the world state has been updated but the confirmed txs have not yet been
        // processed
        confirmed(sender, pendingTransaction.getNonce());
      } else if (senderTxs.firstKey() == pendingTransaction.getNonce()) {
        // it is a cross layer replacement, namely added to a previous layer
        final PendingTransaction replacedTx = senderTxs.pollFirstEntry().getValue();
        processRemove(senderTxs, replacedTx.getTransaction(), CROSS_LAYER_REPLACED);

        if (senderTxs.isEmpty()) {
          txsBySender.remove(sender);
        }
      } else {
        internalNotifyAdded(senderTxs, pendingTransaction);
      }
    }
    nextLayer.notifyAdded(pendingTransaction);
  }
Return the full content of this layer, organized as a list of sender pending txs. For each
sender the collection pending txs is ordered by nonce asc.

@return a list of sender pending txs
ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/transactions/layered/AbstractTransactionsLayer.java