registerThemes(themes) {
    for (var theme in themes) {
      if (themes.hasOwnProperty(theme)) {
        if (typeof themes[theme] === "string") {
          this.registerUrl(theme, themes[theme]);
        } else {
          this.registerRules(theme, themes[theme]);
        }
      }
    }
  }
Register themes object
@param {object} themes