private GTheme readFileTheme() throws IOException {
		try (Reader reader = new FileReader(file)) {
			read(reader);
		}
		if (theme == null) {
			throw new IOException("Invalid Theme file: " + file);
		}
		return theme;
	}
Assumes the file is a theme file and reads it.
Ghidra/Framework/Gui/src/main/java/generic/theme/ThemeReader.java