@Override
  public void onCloseStorage() {
    this.cachedWorldStatesByHash.clear();
  }
Returns the worldstate for the supplied root hash. If the worldstate is not already in cache,
this method will attempt to fetch it and add it to the cache. synchronized to prevent
concurrent loads/adds to the cache of the same root hash.

@param rootHash rootHash to supply worldstate storage for
@return Optional worldstate storage
ethereum/core/src/main/java/org/hyperledger/besu/ethereum/trie/pathbased/common/cache/PathBasedCachedWorldStorageManager.java