public BookManager::addFormElements(array $form, FormStateInterface $form_state, NodeInterface $node, AccountInterface $account, $collapsed = TRUE)
Builds the common elements of the book form for the node and outline forms.
Parameters
array $form: An associative array containing the structure of the form.
\Drupal\Core\Form\FormStateInterface $form_state: The current state of the form.
\Drupal\node\NodeInterface $node: The node whose form is being viewed.
\Drupal\Core\Session\AccountInterface $