def _unopened_notification_index(options = {})
        reverse            = options[:reverse] || false
        with_group_members = options[:with_group_members] || false
        target_index = notifications.unopened_index(reverse, with_group_members).filtered_by_options(options)
        options[:limit].present? ? target_index.limit(options[:limit]) : target_index
      end
def _unopened_notification_index(options = {})
        reverse            = options[:reverse] || false
        with_group_members = options[:with_group_members] || false
        target_index = notifications.unopened_index(reverse, with_group_members).filtered_by_options(options)
        options[:limit].present? ? target_index.limit(options[:limit]) : target_index
      end
Gets unopened notification index of the target as ActiveRecord.
 @api private

 @param [Hash] options Options for notification index
 @option options [Integer]    :limit                  (nil)   Limit to query for notifications
 @option options [Boolean]    :reverse                (false) If notification index will be ordered as earliest first
 @option options [Boolean]    :with_group_members     (false) If notification index will include group members
 @option options [String]     :filtered_by_type       (nil)   Notifiable type for filter
 @option options [Object]     :filtered_by_group      (nil)   Group instance for filter
 @option options [String]     :filtered_by_group_type (nil)   Group type for filter, valid with :filtered_by_group_id
 @option options [String]     :filtered_by_group_id   (nil)   Group instance id for filter, valid with :filtered_by_group_type
 @option options [String]     :filtered_by_key        (nil)   Key of the notification for filter
 @option options [Array|Hash] :custom_filter          (nil)   Custom notification filter (e.g. ["created_at >= ?", time.hour.ago])
 @return [ActiveRecord_AssociationRelation<Notificaion>] Unopened notification index of the target