Trace_stat_summary.Store_watched_nodes_folderAccumulator for the store field of t.
type acc = acc_per_node listval create_acc : int -> acc_per_node listval accumulate :
acc_per_node list ->
[> `Commit of 'a Def.commit_base ] ->
acc_per_node listval finalise : acc_per_node list -> Watched_node.mapval create :
int ->
([> `Commit of 'a Def.commit_base ], acc_per_node list, Watched_node.map)
Utils.Parallel_folders.folder