Default options form that provides the label widget that all fields should have.
Overrides FieldPluginBase::buildOptionsForm
public function buildOptionsForm(&$form, &$form_state) {
parent::buildOptionsForm($form, $form_state);
$form['native_language'] = array(
'#title' => t('Native language'),
'#type' => 'checkbox',
'#default_value' => $this->options['native_language'],
'#description' => t('If enabled, the native name of the language will be displayed'),
);
}