@Override
  public Optional<Bytes> getFlatAccount(
      final Supplier<Optional<Bytes>> worldStateRootHashSupplier,
      final NodeLoader nodeLoader,
      final Hash accountHash,
      final SegmentedKeyValueStorage storage) {
    getAccountCounter.inc();
    Optional<Bytes> response =
        storage.get(ACCOUNT_INFO_STATE, accountHash.toArrayUnsafe()).map(Bytes::wrap);
    if (response.isEmpty()) {
      // after a snapsync/fastsync we only have the trie branches.
      final Optional<Bytes> worldStateRootHash = worldStateRootHashSupplier.get();
      if (worldStateRootHash.isPresent()) {
        response =
            new StoredMerklePatriciaTrie<>(
                    new StoredNodeFactory<>(nodeLoader, Function.identity(), Function.identity()),
                    Bytes32.wrap(worldStateRootHash.get()))
                .get(accountHash);
        if (response.isEmpty()) {
          getAccountMissingMerkleTrieCounter.inc();
        } else {
          getAccountMerkleTrieCounter.inc();
        }
      }
    } else {
      getAccountFoundInFlatDatabaseCounter.inc();
    }

    return response;
  }
This class represents a strategy for reading data from a partial flat database. It extends the
FlatDbReaderStrategy and provides additional functionality for reading data from a merkle trie.
If data is missing in the flat database, this strategy falls back to the merkle trie to retrieve
the data. It adds a fallback mechanism for the `getAccount` and `getStorageValueByStorageSlotKey`
methods, which checks if the data is present in the flat database, and if not, queries the merkle
trie
ethereum/core/src/main/java/org/hyperledger/besu/ethereum/trie/pathbased/bonsai/storage/flat/BonsaiPartialFlatDbStrategy.java