@Override
		public ID getClosestID(URL url) {
			ID closestID = mapDelegate.getClosestID(url);
			if (closestID != null) {
				return closestID; // it's in our map
			}

			LOG.trace("Help Set \"" + GHelpSet.this + "\" does not contain ID for URL: " + url);

			Set<Entry<HelpSet, Map>> entrySet = helpSetsToCombinedMaps.entrySet();
			for (Entry<HelpSet, Map> entry : entrySet) {
				Map map = entry.getValue();
				closestID = map.getClosestID(url);
				if (closestID != null) {
					return closestID;
				}
			}

			LOG.trace("No ID found in any HelpSet for URL: " + url);

			return null;
		}
A special class to allow us to handle help ID lookups across help sets
Ghidra/Framework/Help/src/main/java/help/GHelpSet.java