private void populateCategories(Category parent) {

			categorySet.add(parent.getCategoryPath());
			Category[] children = parent.getCategories();
			for (Category category : children) {
				CategoryPath path = category.getCategoryPath();
				categorySet.add(path);

				populateCategories(category);
			}
		}
Returns a list of the unique Category Paths ({@link CategoryPath}) as utilized by the 
data types open in the current tool.  

@return a list of the {@link CategoryPath} associated with the data types open in the 
current tool.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/datamgr/archive/DataTypeIndexer.java