∀ {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) (e' : OpenPartialHomeomorph Y Z),
  (e.trans e').toPartialEquiv = e.trans e'.toPartialEquiv