PersonAdmin.php

    protected function configureFormFields(FormMapper $formMapper)
    {
        $formMapper->add('firstName', 'text');
        $formMapper->add('surname', 'text');
        $formMapper->add(
            'sex',
            'choice',
            array('choices' => [
                "person.sex0" => 0,
                "person.sex1" => 1,
                "person.sex2" => 2,
            ],
                'expanded' => true,
                'translation_domain' => 'person',
                'label'=>'person.sex'
            )
        );
    }