def comments
      activitable_type =
        ActivityObject.with_activitable_type(type: Comment.name)

      @comments ||= children.joins(:activitable_object)
                            .merge(activitable_type)
    end
def comments
      activitable_type =
        ActivityObject.with_activitable_type(type: Comment.name)

      @comments ||= children.joins(:activitable_object)
                            .merge(activitable_type)
    end
Retrieves the comments for an activity

 @return [ActiveRecord::AssociationRelation] a collection of
 {Socializer::Activity} objects