How to access codeigniter user defined models inside custom library

Question

Possible Duplicate:
How to access codeigniter user defined models

When i want to access a function of a user defined model in codeigniter inside a custom user defined library it throughs

Call to a member function Set_where() on a non-object

Although i load the model by using this inside that library

$CI =& get_instance();

$CI->load->model('home_model');

And im using this code to access the function inside home_model class

$CI->home_model->Set_where("film_feature='Y'");

So now it throughs me the above error.