private void writeReturnType(XmlWriter writer, Function func) {
		DataType rt = func.getReturnType();
		if (rt != null && rt != DataType.DEFAULT) {
			XmlAttributes attrs = new XmlAttributes();
			attrs.addAttribute("DATATYPE", rt.getDisplayName());
			attrs.addAttribute("DATATYPE_NAMESPACE", rt.getCategoryPath().getPath());
			attrs.addAttribute("SIZE", rt.getLength(), true);
			writer.writeElement("RETURN_TYPE", attrs);
		}
	}
Returns the name of function qualified with
any namespace information.
For example, "User32.dll::SomeClass::printf".
Ghidra/Features/Base/src/main/java/ghidra/app/util/xml/FunctionsXmlMgr.java