code: @CardBrand
      public String getBrand() {
          if (StripeTextUtils.isBlank(brand) && !StripeTextUtils.isBlank(number)) {
              brand = CardUtils.getPossibleCardType(number);
          }
  
          return brand;
      }
docs: Gets the {@link #brand} of this card. Updates the value if none has yet been set, or
  if the {@link #number} has been changed.
  
  @return the {@link #brand} of this card