The fact that you can define custom attributes and place them in your source code would be of little value without some way of retrieving that information and acting on it. This means that instances of custom attributes cannot be created, because that would require executing their constructors. Let’s look take a closer look at the defer attribute. Idempotent Laurent polynomials (in noncommuting variables), Sci-fi book in which people can photosynthesize with their hair, Print a conversion table for (un)signed bytes. Input and Select. The formmethod attribute works with the following input types: submit and image.. HTML