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 $formMapper
            ->get('realRoles')
            ->addModelTransformer(new StringToArrayTransformer());
            ->addEventListener(FormEvents::PRE_SET_DATA, function(FormEvent $event) {
            $form = $event->getForm();
            $data = $event->getData();
            $qw = 2;
            $result = array();
            if ($data) {
                foreach ($data as $key => $value) {
                    $result[] = array(
                        'key' => $key,
                        'value' => $value
                    );
                }
            }

            $event->setData($result);
        }, 1);