code: protected Type getValueGenericType(AnnotatedElement element) {
          if (element instanceof Field) {
              return ((Field) element).getGenericType();
          }
          if (element instanceof Method) {
              return ((Method) element).getGenericReturnType();
          }
          throw new PropertyLoaderException("Could not get generic type for element");
      }
docs: Returns the generic type of the value for given element. {@link Field} and {@link Method}
  are only supported.