Prevents book module from being uninstalled whilst any book nodes exist or there are any book outline stored. Hierarchy

public BookNavigationCacheContext::

Books Array. Type:

public BookManager::loadBookLink($nid, $translate = TRUE)

public BookController::bookRender()

public BookManagerInterface::getBookParents(array $item

public BookAdminEditForm::submitForm(array &$form,

The book being displayed. Type:

protected BookManager::doBookTreeBuild($bid, array $parameters = array())

protected BookManager::setParents(array &$link, array $parent)