class EntityType extends DoctrineType
{
    // ...

/**
 * @param Options $options
 * @return ObjectManager
 */    
    public function getEntityManager( Options $options )
    {
    if( null === $options['em'] )
    {
        $em =   $this->registry->getManagerForClass( $options['class'] );
    }
    else if( $options['em'] instanceof ObjectManager )
    {
        $em =   $options['em'];   
    }
    else
    {
        $em =   $this->registry->getManager( $options['em'] );
    }   

    return $em;
    }     

    public function getDefaultOptions()
    {
        $type = $this;

        $loader = function (Options $options) use ($type) {
            if (null !== $options['query_builder']) {
                $manager = $type->getEntityManager($options);

                return $type->getLoader($manager, $options['query_builder'], $options['class']);
            }

            return null;
        };

        $choiceList = function (Options $options) use ($type) {
            $manager = $type->getEntityManager($options);

            return new EntityChoiceList(
                $manager,
                $options['class'],
                $options['property'],
                $options['loader'],
                $options['choices'],
                $options['group_by']
            );
        };

        return array(
            'loader'            => $loader,
            'choice_list'       => $choiceList,
        ) + parent::getDefaultOptions();    
    }
}