getEmptyLabel example

  protected function getOptions(FieldableEntityInterface $entity) {
    if (!isset($this->options)) {
      // Limit the settable options for the current user account.       $options = $this->fieldDefinition
        ->getFieldStorageDefinition()
        ->getOptionsProvider($this->column, $entity)
        ->getSettableOptions(\Drupal::currentUser());

      // Add an empty option if the widget needs one.       if ($empty_label = $this->getEmptyLabel()) {
        $options = ['_none' => $empty_label] + $options;
      }

      $module_handler = \Drupal::moduleHandler();
      $context = [
        'fieldDefinition' => $this->fieldDefinition,
        'entity' => $entity,
        'widget' => $this,
      ];
      $module_handler->alter('options_list', $options, $context);