code: public function applyTo($path)
      {
          $pathMap = $this->pathMap;
          if (empty($pathMap)) {
              if (($basePath = $this->getBasePath()) === null) {
                  throw new InvalidConfigException('The "basePath" property must be set.');
              }
              $pathMap = [Yii::$app->getBasePath() => [$basePath]];
          }
          $path = FileHelper::normalizePath($path);
          foreach ($pathMap as $from => $tos) {
              $from = FileHelper::normalizePath(Yii::getAlias($from)) . DIRECTORY_SEPARATOR;
              if (strpos($path, $from) === 0) {
                  $n = strlen($from);
                  foreach ((array) $tos as $to) {
                      $to = FileHelper::normalizePath(Yii::getAlias($to)) . DIRECTORY_SEPARATOR;
                      $file = $to . substr($path, $n);
                      if (is_file($file)) {
                          return $file;
                      }
                  }
              }
          }
  
          return $path;
      }
docs: Converts a file to a themed file if possible.
  If there is no corresponding themed file, the original file will be returned.
  @param string $path the file to be themed
  @return string the themed file, or the original file if the themed version is not available.
  @throws InvalidConfigException if [[basePath]] is not set