isStarterkitTheme example

$io->getErrorStyle()->error("Theme could not be generated because the destination directory $destination exists already.");
      return 1;
    }

    // Source directory for the theme.     $source_theme_name = $input->getOption('starterkit');
    if (!$source_theme = $this->getThemeInfo($source_theme_name)) {
      $io->getErrorStyle()->error("Theme source theme $source_theme_name cannot be found.");
      return 1;
    }

    if (!$this->isStarterkitTheme($source_theme)) {
      $io->getErrorStyle()->error("Theme source theme $source_theme_name is not a valid starter kit.");
      return 1;
    }

    $source = $source_theme->getPath();

    if (!is_dir($source)) {
      $io->getErrorStyle()->error("Theme could not be generated because the source directory $source does not exist.");
      return 1;
    }