Method unlock

/**
 * Unlock cached item
 *
 * @param   string  $id     The cache data ID
 * @param   string  $group  The cache data group
 *
 * @return  boolean
 *
 * @since   3.5
 */
public function unlock($id, $group = null)
{
    $cache_id = $this->_getCacheId($id, $group) . '_lock';
    // The apcu_delete function returns false if the ID does not exist
    if (apcu_exists($cache_id)) {
        return apcu_delete($cache_id);
    }
    return true;
}