authenticate problem

Hello,

My old coder added in all my funtions this code in start. 

admin_authenticate();


for exmple :
function enable()
{
admin_authenticate();

$this->db->where("category_id", $this->uri->segment(4));
$this->db->update("categories", array("category_enabled" => $this->uri->segment(5)));

$msg = $this->uri->segment(5)? "enabled" : "disabled";

redirect("admins/categories/listing/".$msg);
}




My question is where admin_authenticate();  ??? i wana edit this for redirect page ? please help i m new.