getUniqueTmpDirPath example

$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;
    }

    $tmp_dir = $this->getUniqueTmpDirPath();
    $this->copyRecursive($source, $tmp_dir);

    // Readme is specific to Starterkit, so remove it from the generated theme.     $readme_file = "$tmp_dir/README.md";
    if (!file_put_contents($readme_file, "$destination_theme theme, generated from $source_theme_name. Additional information on generating themes can be found in the [Starterkit documentation](https://www.drupal.org/docs/core-modules-and-themes/core-themes/starterkit-theme).")) {
      $io->getErrorStyle()->error("The readme could not be rewritten.");
      return 1;
    }

    // Rename files based on the theme machine name.     $file_pattern = "/$source_theme_name\.(theme|[^.]+\.yml)/";