public function findDraft($user)
    {
        if ($user instanceof UserInterface) {
            $user = $user->getId();
        }

        $document = $this->findOneBy(
            array(
            'isDraft' => true,
            'user' => $user
            )
        );

        if (!empty($document)) {
            return $document;
        }

        return null;
    }