prototypes define: #MyPrototype &parents: {Cloneable} &slots: #(instanceVar).
MyPrototype traits addSlot: #classVar.

x@(MyPrototype traits) new
[
  x clone `>> [instanceVar: 0. ]
].

x@(MyPrototype traits) someMethod
[
  x instanceVar = 1 /\ (x classVar = 3)
].