sig type ('k, 'v) t = ('k, 'v) Core.Std.Map.Poly.t val filter_mapi : ('k, 'v1) t -> f:(key:'k -> data:'v1 -> 'v2 option Deferred_intf.Deferred.t) -> ('k, 'v2) t Deferred_intf.Deferred.t end