getPluginForm example

    }
    // Passing available contexts to the layout plugin here could result in an     // exception since the layout may not have a context mapping for a required     // context slot on creation.     $this->layout = $section->getLayout();

    $form_state->setTemporaryValue('gathered_contexts', $this->getPopulatedContexts($this->sectionStorage));
    $form['#tree'] = TRUE;
    $form['layout_settings'] = [];
    $subform_state = SubformState::createForSubform($form['layout_settings'], $form, $form_state);
    $form['layout_settings'] = $this->getPluginForm($this->layout)->buildConfigurationForm($form['layout_settings'], $subform_state);

    $form['actions']['submit'] = [
      '#type' => 'submit',
      '#value' => $this->isUpdate ? $this->t('Update') : $this->t('Add section'),
      '#button_type' => 'primary',
    ];
    if ($this->isAjax()) {
      $form['actions']['submit']['#ajax']['callback'] = '::ajaxSubmit';
      // @todo static::ajaxSubmit() requires data-drupal-selector to be the same       // between the various Ajax requests. A bug in       // \Drupal\Core\Form\FormBuilder prevents that from happening unless

public function doBuildForm(array $form, FormStateInterface $form_state, SectionStorageInterface $section_storage = NULL, $delta = NULL, SectionComponent $component = NULL) {
    $this->sectionStorage = $section_storage;
    $this->delta = $delta;
    $this->uuid = $component->getUuid();
    $this->block = $component->getPlugin();

    $form_state->setTemporaryValue('gathered_contexts', $this->getPopulatedContexts($section_storage));

    $form['#tree'] = TRUE;
    $form['settings'] = [];
    $subform_state = SubformState::createForSubform($form['settings'], $form, $form_state);
    $form['settings'] = $this->getPluginForm($this->block)->buildConfigurationForm($form['settings'], $subform_state);

    $form['actions']['submit'] = [
      '#type' => 'submit',
      '#value' => $this->submitLabel(),
      '#button_type' => 'primary',
    ];
    if ($this->isAjax()) {
      $form['actions']['submit']['#ajax']['callback'] = '::ajaxSubmit';
      // @todo static::ajaxSubmit() requires data-drupal-selector to be the same       // between the various Ajax requests. A bug in       // \Drupal\Core\Form\FormBuilder prevents that from happening unless

  public function form(array $form, FormStateInterface $form_state) {
    $entity = $this->entity;

    // Store the gathered contexts in the form state for other objects to use     // during form building.     $form_state->setTemporaryValue('gathered_contexts', $this->contextRepository->getAvailableContexts());

    $form['#tree'] = TRUE;
    $form['settings'] = [];
    $subform_state = SubformState::createForSubform($form['settings'], $form, $form_state);
    $form['settings'] = $this->getPluginForm($entity->getPlugin())->buildConfigurationForm($form['settings'], $subform_state);
    $form['visibility'] = $this->buildVisibilityInterface([], $form_state);

    // If creating a new block, calculate a safe default machine name.     $form['id'] = [
      '#type' => 'machine_name',
      '#maxlength' => 64,
      '#description' => $this->t('A unique name for this block instance. Must be alpha-numeric and underscore separated.'),
      '#default_value' => !$entity->isNew() ? $entity->id() : $this->getUniqueMachineName($entity),
      '#machine_name' => [
        'exists' => '\Drupal\block\Entity\Block::load',
        'replace_pattern' => '[^a-z0-9_.]+',