public function getMainPrefixAndPath(Dir $rootDir) {
    $prefixesPaths = $this->getPrefixes();
    $prefixes = array_keys($prefixesPaths);
    
    if (count($prefixes) > 0) {
      $firstPrefixPaths = array_shift($prefixesPaths);

      $path = array_shift($firstPrefixPaths);
      $dir = $path instanceof Dir ? $path : $rootDir->sub($path);
    
      return array(array_shift($prefixes), $dir);
    }
    
    throw new NoAutoLoadPrefixException('Cannot retrieve the main Prefix and Library Path from AutoLoadInfo. AutoLoadInfo is defined: '.print_r($prefixesPaths, true)."\nPlease insert autoload informations into your composer.json");
  }