∀ {α : Type u_1} {β : Type u_3} {γ : Type u_2} [inst : TopologicalSpace α] [inst_1 : TopologicalSpace β]
  [inst_2 : TopologicalSpace γ] (f : β →CO γ) (g : α →CO β), IsOpenMap (f.toFun ∘ ⇑g.toContinuousMap)