/**
  * Makes sure the payment method is related to the specified payment method
  *
  * @param EE_Payment_Method $payment_method
  * @return EE_Payment_Method
  * @throws \EE_Error
  */
 public function set_usable_currencies_on_payment_method($payment_method)
 {
     foreach ($payment_method->get_all_usable_currencies() as $currency_obj) {
         $payment_method->_add_relation_to($currency_obj, 'Currency');
     }
     return $payment_method;
 }