Trad dans la classe du module

[bayzazi]

Bonjour à tous

Comment gérer la traduction des textes affectés dans la classe du module ?
Pour un module donné, la fonction suivante :

private function _getError(){

       if ($this->errorPaymentNumber == 101)
           $this -> errorPayment = $this -> l('Declined by Bank');
       elseif($this->errorPaymentNumber == 102)
           $this -> errorPayment = $this -> l("Referral by Bank (treat as decline in automated system such as internet)");
       elseif($this->errorPaymentNumber == 103)
           $this -> errorPayment = $this -> l("Card reported lost or stolen");
       elseif($this->errorPaymentNumber >= 200 AND $this->errorPaymentNumber<300)
           $this -> errorPayment = $this -> l("Error with bank systems");
       elseif($this->errorPaymentNumber >= 300 AND $this->errorPaymentNumber<400)
           $this -> errorPayment = $this -> l("Error with Realex Payments systems");
       elseif($this->errorPaymentNumber >= 500 AND $this->errorPaymentNumber<600)
           $this -> errorPayment = $this -> l("Incorrect XML message formation or content");
       elseif($this->errorPaymentNumber == 666)
           $this -> errorPayment = $this -> l("Client deactivated.");
       else
           $this -> errorPayment = $this -> l("A problem occured in your paiement");
   }

Dans le backoff, pas trace de ces textes pour les traduire en français. Comment gérer ça ?
Merci