how can i use CI's library into myLibrary ?

[eluser]arlabbafi[/eluser]
can i use CI's library in myLibrary ?
Because i want use session Library into my Library But Does not work and show me an error

<h4>A PHP Error was encountered</h4>

<p>Severity: Notice</p>
<p>Message: Undefined property: MyFunctions::$session</p>
<p>Filename: libraries/MyFunctions.php</p>
<p>Line Number: 51</p>

<br />
<b>Fatal error</b>: Call to a member function userdata() on a non-object in <b>C:\xampp\htdocs\CI\system\application\libraries\MyFunctions.php</b> on line <b>51</b><br />

[eluser]flaky[/eluser]
are you doing this

Code:

$ci =& get_instance();
$ci->session->userdata('something');

?