∀ {X : Type u_1} {Y : Type u_3} {Z : Type u_5} [inst : TopologicalSpace X] [inst_1 : TopologicalSpace Y]
  [inst_2 : TopologicalSpace Z] (e : OpenPartialHomeomorph X Y) (f' : Y ≃ₜ Z), (e.transHomeomorph f').source = e.source