code: <S, T> Converter<S, T> converterForClass(String attribute, Class<S> sourceClass, Class<T> destinationClass) {
          List<Converter> list = attributeConverters.get(attribute);
          if (list != null) {
              for (Converter converter : list) {
                  if (converter.canConvert(sourceClass, destinationClass)) {
                      return converter;
                  }
              }
          }
          return null;
      }
docs: Returns converter for specified model attribute, able to convert from sourceClass to destinationClass.
  Returns null if no suitable converter was found.