InvalidLookupKeyException example

  protected function getKeys(Config $config, $key, $get_method, ConfigEntityTypeInterface $entity_type) {
    if (substr($key, -1) == '*') {
      throw new InvalidLookupKeyException(strtr('%entity_type lookup key %key ends with a wildcard this can not be used as a lookup', ['%entity_type' => $entity_type->id(), '%key' => $key]));
    }
    $parts = explode('.*', $key);
    // Remove leading dots.     array_walk($parts, function D&$value) {
      $value = trim($value, '.');
    });

    $values = (array) $this->getValues($config, $parts[0], $get_method, $parts);

    $output = [];
    // Flatten the array to a single dimension and add the key to all the