code: public void addAttributeBuilder(Class<? extends Attribute> clazz, AttributeWidgetBuilder builder) {
  		builders.put(clazz, builder);
  	}
docs: Add an attribute builder to the collection. Attributes with the given class will
  have their widgets build by this builder.
  <p/>
  If there is already a builder for the given class it will be overwritten.
  
  @param clazz   the class of the attribute that is handled by the builder.
  @param builder the builder.