Method clean

/**
 * Clean cache for a group given a mode.
 *
 * group mode    : cleans all cache in the group
 * notgroup mode : cleans all cache not in the group
 *
 * @param   string  $group  The cache data group
 * @param   string  $mode   The mode for cleaning cache [group|notgroup]
 *
 * @return  boolean
 *
 * @since   1.7.0
 */
public function clean($group, $mode = null)
{
    return true;
}