ContentEntityForm::form

public ContentEntityForm::form(array $form, FormStateInterface $form_state)

public function form(array $form, FormStateInterface $form_state) {
  $form = parent::form($form, $form_state);
  // Content entity forms do not use the parent's #after_build callback
  // because they only need to rebuild the entity in the validation and the
  // submit handler because Field API uses its own #after_build callback for
  // its widgets.
  unset($form['#after_build']);

  $this->getFormDisplay($form_state)->buildForm($this->entity, $form, $form_state);
  // Allow modules to act before and after form language is updated.
  $form['#entity_builders']['update_form_langcode'] = [$this, 'updateFormLangcode'];
  return $form;
}