final void promoteTransactions() {
    final int freeSlots = maxTransactionsNumber() - pendingTransactions.size();
    final long freeSpace = cacheFreeSpace();

    if (freeSlots > 0 && freeSpace > 0) {
      nextLayer
          .promote(
              this::promotionFilter, cacheFreeSpace(), freeSlots, getRemainingPromotionsPerType())
          .forEach(addedTx -> processAdded(addedTx, AddReason.PROMOTED));
    }
  }
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