jumika

Selectize.define( 'clear_selection', function ( options ) {
    var self = this;
    var settings = $.extend({
        title: 'Clear selection'
    }, options);

    //Overriding because, ideally you wouldn't use header & clear_selection simultaneously
    self.plugins.settings.dropdown_header = {
        title: settings.title
    };

jumika

<?php
use Symfony\Component\Form\AbstractTypeExtension;
use Symfony\Component\OptionsResolver\OptionsResolverInterface;
use Symfony\Component\Form\FormBuilderInterface;
class CollectionPrototypeDataTypeExtension extends AbstractTypeExtension {
	public function buildForm(FormBuilderInterface $builder, array $options) {
		parent::buildForm($builder, $options);
		if(($prototypeFormBuilder = $builder->getAttribute('prototype')) && isset($options['prototype_data'])) {
			$prototypeFormBuilder->setData($options['prototype_data']);
		}