@Override
      public boolean hasNext() {
        return currentStaticRangeTransaction.isPresent()
            || currentDynamicRangeTransaction.isPresent();
      }
See this post for an explainer about these data structures:
https://hackmd.io/@adietrichs/1559-transaction-sorting
ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/transactions/sorter/BaseFeePendingTransactionsSorter.java