anchor.diff:          ChainedClassNew "Hierarchy" <| fun chained ->
           [
               "nodes"    => HierarchyNode?root ^-> !|HierarchyNode
  -            "links"    => getSetVal chained !|(Link HierarchyNode)
  +            "links"    => getSetVal chained !|Link.[HierarchyNode]
               "children" => getSetVal chained (Obj ^-> Obj)
               "sort"     => getSetVal chained Comparator
               "value"    => getSetVal chained (Obj ^-> Float)
  
positive.code:                 "treemap"   => O ^-> Treemap
              ]
              Class "d3.scale"
              |+> [
                  "linear"    => O ^-> QuantitativeScale
                  "sqrt"      => O ^-> QuantitativeScale
                  "pow"       => O ^-> QuantitativeScale
  
negative.code: 
      let TimeFormat =
          Class "TimeFormat"
          |+> Instance [
              "apply" => Date?date ^-> String
              "parse" => String?string ^-> Date
          ]
  