code: public String code(final String code) {
          if (this.theme == null) {
              throw new TemplateProcessingException("Theme cannot be resolved because RequestContext was not found. "
                  + "Are you using a Context object without a RequestContext variable?");
          }
          return this.theme.getMessageSource().getMessage(code, null, "", this.locale);
      }
docs: Looks up and returns the value of the given key in the properties file of
  the currently-selected theme.
  
  @param code Key to look up in the theme properties file.
  @return The value of the code in the current theme properties file, or an
  empty string if the code could not be resolved.