How can I know if a model exist

I answer myself just in case anyone have the same problem

Just add a modification in MY_Model constructor

if(!empty($tatic::$table_name)
static::$fields = get_fields();

After that, add a set_data($table) function

And there we go:

if(!class_exist(ucfirst(static::$prefix) . 'M'){

$this->load->model('nomenclators_m');
$this->nomenclators_m->set_data(trim(static::$prefix, '_'));