field_group-8.x-3.1/modules/field_group_accordion/field_group_accordion.module

<?php

/**
 * @file
 * Module file for field_group_accordion.
 */

/**
 * Implements hook_theme().
 */
function field_group_accordion_theme() {
  return [
    'field_group_accordion_item' => [
      'render element' => 'element',
      'template' => 'field-group-accordion-item',
      'file' => 'templates/theme.inc',
    ],
    'field_group_accordion' => [
      'render element' => 'element',
      'template' => 'field-group-accordion',
      'file' => 'templates/theme.inc',
    ],
  ];
}