public Map<Transaction, TransactionSelectionResult> getNotSelectedTransactions() {
    return Map.copyOf(notSelectedTransactions);
  }
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