Symfony2 - 在ORM DQL表单中设置复选框的值

我正在创建一个表单，该表单应该使用LexikFilter Bundle过滤Symfony2（ver 2.3）中的自定义查询列表。
项目设置：

1. Symfony2 ：2.3.7
2. 词典过滤器包：3.0.8
3. 教义ORM 2.4

该项目由具有n：m关系的实体组成（家长培训），父过滤器表单嵌入了培训过滤器表单，如下所示：

class MyParentsType extends AbstractType
{
    private $repository ;
    function __construct($repository)
    {
        $this->repository = $repository; // store it, we are going to use it later
    }
    public function getName()
    {
        return 'parents_filter';
    }
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder->add('Firstname', 'filter_text', array('condition_pattern' => FilterOperands::STRING_BOTH,))
                ->add('Lastname', 'filter_text', array('condition_pattern' => FilterOperands::STRING_BOTH,))
                ->add('trainings','filter_collection_adapter', array(
                                            'type'=> new MyTrainingType2($this->repository),
                                            'default_data' => new ArrayCollection(),
                                            'add_shared'=> function(FilterBuilderExecuterInterface $qbe){
                                                $closure = function(QueryBuilder $filterBuilder, $alias, $joinAlias, Expr $expr){
                                                     $filterBuilder ->leftJoin($alias.'.options',$joinAlias);
                                                };
                                                $qbe->addOnce($qbe->getAlias().'.options','opt',$closure);
                                            },
                ));
    }
    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setDefaults(
            [
                'data_class' =>'tuto'LexikTestBundle'Entity'Parents',
                'csrf_protection' => false,
                'validation_groups' => ['filtering'] // avoid NotBlank() constraint-related message
            ]
        );
    }

和训练筛选器窗体：

class MyTrainingType2 extends AbstractType
{
    private $repository ;
    function __construct($repository)
    {
        $this->repository = $repository; // store it, we are going to use it later
    }

    public function getName()
    {
        return 'training_filter';
    }
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder->add('Title', 'filter_text', array('condition_pattern' => FilterOperands::STRING_BOTH,))
                ->add('Location', 'filter_choice', array( 'choice_list' => new ChoiceList($this->repository->getLocationList(),$this->repository->getLocationList()),
                                                          'expanded'=> true,
                                                          'multiple'=>true,
                                                          )
                    );
    }
    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setDefaults(
            [
                'data_class' =>'tuto'LexikTestBundle'Entity'Training',
                'csrf_protection' => false,
                'validation_groups' => ['filtering'] // avoid NotBlank() constraint-related message
            ]
        );
    }
}  

这是Training Repository的getLocationList()方法：

 public function getLocationList()
    {   $qb = $this->createQueryBuilder('t')
        ->select('t.Location')//
        ->orderBy('t.Location','asc')
        ->distinct(true);
        return $qb->getQuery()->getArrayResult();
    }

筛选器确实显示复选框，但值字段设置为列名 Location 。下面是getArrayResult返回的数组片段

array (size=199)
  0 => 
    array (size=1)
      'Location' => string '‘Arīshah' (length=11)
  1 => 
    array (size=1)
      'Location' => string 'Abuja' (length=5)

我想将其返回为：

 0 => 
    array (size=1)
      '‘Arīshah' => string '‘Arīshah' (length=11)
  1 => 
    array (size=1)
      'Abuja' => string 'Abuja' (length=5)