             (1) J.AutoDict [tag], keysFunc, valueFunc, [onChange, [options]]
             (2) J.AutoDict [tag], keysList, valueFunc, [onChange, [options]]
             (3) J.AutoDict [tag], fieldSpecs, [onChange, [options]]
+
+            Options:
+                creator
+                onChange
+                withFieldFuncs
+                fineGrained
+                filterFunc
+                    Pretend like the only keys are ones whose corresponding
+                    value passes filterFunc
         ###
 
         unless @ instanceof J.AutoDict


        @keysFunc = keysFunc
        @valueFunc = valueFunc

        @_keysVar = J.AutoVar(
            (

            @_hasKeyDeps[key] ?= new Tracker.Dependency @creator
            @_hasKeyDeps[key].depend()

        if _filtered and @filterFunc?
            key of @_fields and @tryGet(key) isnt undefined
        else
            key of @_fields


    isActive: ->
