/**
 * Implements hook_field_delete().
 */
function {{ machine_name }}_field_delete($entity_type, $entity, $field, $instance, $langcode, &$items) {
  list($id, $vid, $bundle) = entity_extract_ids($entity_type, $entity);
  foreach ($items as $delta => $item) {
    // For hook_file_references(), remember that this is being deleted.
    $item['file_field_name'] = $field['field_name'];
    // Pass in the ID of the object that is being removed so all references can
    // be counted in hook_file_references().
    $item['file_field_type'] = $entity_type;
    $item['file_field_id'] = $id;
    file_field_delete_file($item, $field, $entity_type, $id);
  }
}