/**
  *    class constructor
  *
  * @access    private
  * @return \EEH_Autoloader
  */
 private function __construct()
 {
     if (self::$_autoloaders === null) {
         self::$_autoloaders = array();
         $this->_register_custom_autoloaders();
         spl_autoload_register(array($this, 'espresso_autoloader'));
     }
 }