@Override
	public int hashCode() {
		int result = history.hashCode();
		result = 31 * result + backing.hashCode();
		return result;
	}
History contains a stack of prior states of items.
If an item has not been modified there is no entry in this map.

@return Map of historical states of items within this bundle.
recaf-core/src/main/java/software/coley/recaf/workspace/model/bundle/BasicBundle.java