public TrieLogLayer addStorageChange(
      final Address address,
      final StorageSlotKey slot,
      final UInt256 oldValue,
      final UInt256 newValue) {
    checkState(!frozen, "Layer is Frozen");
    storage
        .computeIfAbsent(address, a -> new TreeMap<>())
        .put(slot, new PathBasedValue<>(oldValue, newValue));
    return this;
  }
Locks the layer so no new changes can be added;
ethereum/core/src/main/java/org/hyperledger/besu/ethereum/trie/pathbased/common/trielog/TrieLogLayer.java