Method __construct

/**
 * Constructor
 *
 * @param   DatabaseDriver  $db  A database connector object
 *
 * @since   3.1
 */
public function __construct(DatabaseDriver $db)
{
    parent::__construct('#__ucm_content', 'core_content_id', $db);
    $this->setColumnAlias('published', 'core_state');
    $this->setColumnAlias('checked_out', 'core_checked_out_user_id');
    $this->setColumnAlias('checked_out_time', 'core_checked_out_time');
}