public String toTraceLog() {
    return "cumulativeGasUsed="
        + cumulativeGasUsed
        + ", selectedTransactions="
        + selectedTransactions.stream()
            .map(Transaction::toTraceLog)
            .collect(Collectors.joining("; "))
        + ", notSelectedTransactions="
        + notSelectedTransactions.entrySet().stream()
            .map(e -> e.getValue() + ":" + e.getKey().toTraceLog())
            .collect(Collectors.joining(";"));
  }
Access to this field needs to be guarded, since it is possible to read it while another
processing thread is writing, when the selection time is over.
ethereum/blockcreation/src/main/java/org/hyperledger/besu/ethereum/blockcreation/txselection/TransactionSelectionResults.java