Accessing CI object from Library

Hi, 
most of the times I see CI object is accessed from library in following way:

PHP Code:

$ci = &get_instance(); 


But in Codeigntier Ion Auth library they accessed as if they not in library.
Here is contructor of Ion Auth Library.

PHP Code:

    public function __construct()
    {
        $this->config->load('ion_auth', TRUE);
        $this->load->library(array('email'));
//...
} 


How it is accessed using $this in this library?
The link to code: https://github.com/benedmunds/CodeIgnite...n_auth.php