code: private function setThemeFolder($basePath = null)
      {
          $this->themesFolder = $basePath ?: themes_base_path();
  
          if (! is_dir($this->themesFolder)) {
              throw new MissingThemesFolder($this->themesFolder);
          }
      }
docs: @param null|string $basePath
  
  @throws \ThemeManager\Exceptions\MissingThemesFolder - When themes folder does not exist