@Nonnull
	@Override
	public Set<String> getDirtyKeys() {
		Set<String> dirty = new TreeSet<>();
		history.forEach((key, itemHistory) -> {
			if (itemHistory.size() > 1) {
				dirty.add(key);
			}
		});
		return dirty;
	}
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