/**
 * Implements hook_field_widget_form().
 */
function {{ machine_name }}_field_widget_form(&$form, &$form_state, $field, $instance, $langcode, $items, $delta, $element) {
  $element += array(
    '#type' => $instance['widget']['type'],
    '#default_value' => isset($items[$delta]) ? $items[$delta] : '',
  );
  return array('value' => $element);
}