code: public function convert($asset, $basePath)
      {
          $pos = strrpos($asset, '.');
          if ($pos !== false) {
              $ext = substr($asset, $pos + 1);
              if (isset($this->commands[$ext])) {
                  list($ext, $command) = $this->commands[$ext];
                  $result = substr($asset, 0, $pos + 1) . $ext;
                  if ($this->forceConvert || @filemtime("$basePath/$result") < @filemtime("$basePath/$asset")) {
                      $this->runCommand($command, $basePath, $asset, $result);
                  }
  
                  return $result;
              }
          }
  
          return $asset;
      }
docs: Converts a given asset file into a CSS or JS file.
  @param string $asset the asset file path, relative to $basePath
  @param string $basePath the directory the $asset is relative to.
  @return string the converted asset file path, relative to $basePath.