public function render($depth = 0, $indent = null, $inner = false)
    {
        if (!($this->hasChildren())) {
            $this->prepare();
        }
        foreach ($this->fieldsets as $fieldset) {
            foreach ($fieldset->getAllFields() as $field) {
                if ($field instanceof Element\Input\File) {
                    $this->setAttribute('enctype', 'multipart/form-data');
                    break;
                }
            }
        }
        return parent::render($depth, $indent, $inner);
    }