public static FlatDbMode fromVersion(final Bytes version) {
    return Stream.of(FlatDbMode.values())
        .filter(mode -> mode.getVersion().equals(version))
        .findFirst()
        .orElseThrow(
            () -> new IllegalArgumentException("Unknown flat DB mode version: " + version));
  }
The FlatDbMode enum represents the different modes of the flat database. It has two modes:
PARTIAL and FULL.

<p>- PARTIAL: Not all the leaves are present inside the flat database. The trie serves as a
fallback to retrieve missing data. The PARTIAL mode is primarily used for backward compatibility
purposes, where the flat database may not have all the required data, and the trie is utilized to
fill in the gaps.

<p>- FULL: The flat database contains the complete representation of the world state, and there
is no need for a fallback mechanism. The FULL mode represents a fully synchronized state where
the flat database encompasses all the necessary data.
ethereum/core/src/main/java/org/hyperledger/besu/ethereum/worldstate/FlatDbMode.java