docs: public static void applyThemeClass(BaseUIComponent component, IThemeClass... themeClasses) {
          StringBuilder sb = new StringBuilder();
  
          for (IThemeClass themeClass : themeClasses) {
              String cls = themeClass == null ? null : themeClass.getThemeClass();
  
              if (cls != null) {
                  sb.append(sb.length() > 0 ? " " : "").append(themeClass.getThemeClass());
              }
          }
  
          component.addClass(sb.toString());
      }