groups_for

# File activesupport/lib/active_support/notifications/fanout.rb, line 196
      def groups_for(name) # :nodoc:
        silenceable_groups, groups = @groups_for.compute_if_absent(name) do
          listeners = all_listeners_for(name)
          listeners.partition(&:silenceable).map { |l| group_listeners(l) }
        end

        unless silenceable_groups.empty?
          silenceable_groups.each do |group_class, subscriptions|
            active_subscriptions = subscriptions.reject { |s| s.silenced?(name) }
            unless active_subscriptions.empty?
              groups = groups.dup if groups.frozen?
              base_groups = groups[group_class]
              groups[group_class] = base_groups ? base_groups + active_subscriptions : active_subscriptions
            end
          end
        end

        groups
      end