MarkerSetCacheEntry get(Program program) {
			if (program == null || program.isClosed()) {
				return null;
			}
			MarkerSetCacheEntry entry = map.computeIfAbsent(program, this::newEntry);
			if (program.isClosed()) {
				map.remove(program);
				return null;
			}
			return entry;
		}
A LRU map that maintains <i>insertion-order</i> iteration over the elements. As new items are
added, the older items will be removed from this map the given plugin.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/marker/MarkerManager.java