Popsu-coloque/web/core/modules/config/tests/config_schema_test/config_schema_test.module

<?php

/**
 * @file
 * Tests configuration schema functionality.
 */

/**
 * Implements hook_config_schema_info_alter().
 */
function config_schema_test_config_schema_info_alter(&$definitions) {
  if (\Drupal::state()->get('config_schema_test_exception_add')) {
    $definitions['config_schema_test.hook_added_definition'] = $definitions['config_schema_test.hook'];
  }
  if (\Drupal::state()->get('config_schema_test_exception_remove')) {
    unset($definitions['config_schema_test.hook']);
  }

  // Since code can not be unloaded only alter the definition if it exists.
  if (isset($definitions['config_schema_test.hook'])) {
    $definitions['config_schema_test.hook']['additional_metadata'] = 'new schema info';
  }
}