comment how updates should work

src/observable/map/MappedMap.js

@@ -1,5 +1,8 @@
 import BaseObservableMap from "./BaseObservableMap.js";
-
+/*
+so a mapped value can emit updates on it's own with this._updater that is passed in the mapping function
+how should the mapped value be notified of an update though? and can it then decide to not propagate the update?
+*/
 export default class MappedMap extends BaseObservableMap {
     constructor(source, mapper) {
         super();