BookManager::deleteFromBook

public BookManager::deleteFromBook($nid)

public function deleteFromBook($nid) {
  $original = $this->loadBookLink($nid, FALSE);
  $this->bookOutlineStorage->delete($nid);

  if ($nid == $original['bid']) {
    // Handle deletion of a top-level post.
    $result = $this->bookOutlineStorage->loadBookChildren($nid);
    $children = $this->entityManager->getStorage('node')->loadMultiple(array_keys($result));
    foreach ($children as $child) {
      $child->book['bid'] = $child->id();
      $this->updateOutline($child);
    }
  }
  $this->updateOriginalParent($original);
  $this->books = NULL;
  Cache::invalidateTags(array('bid:' . $original['bid']));
}