function polaris_drupal_taxonomy_form_alter(&$form, FormStateInterface &$form_state, $form_id) {
  $term = Drupal::entityManager()->getStorage('taxonomy_term')->loadTree("article_type");;
  kint($term);
  switch ($form_id) {

    case 'taxonomy_term_category_form':
    case 'taxonomy_term_article_type_form':
    case 'taxonomy_term_main_purpose_form':
    case 'taxonomy_term_tags_form':
    case 'taxonomy_term_content_partnership_form':
    case 'taxonomy_term_traffic_source_form':
    case 'taxonomy_term_client_form':
      $form['field_index_page']['widget']['value']['#default_value'] = true;
  }
}