∀ {R : Type u_2} [inst : CommRing R] {S : Type u_4} [inst_1 : CommRing S] {υ : Type u_5} {T : Type u_6}
  [inst_2 : CommRing T] [inst_3 : Algebra R S] [inst_4 : Algebra R T] [inst_5 : Algebra S T] {a : PowerSeries S}
  {b : MvPowerSeries υ T} [inst_6 : IsScalarTower R S T] (ha : PowerSeries.HasSubst a) (hb : PowerSeries.HasSubst b),
  (AlgHom.restrictScalars R (PowerSeries.substAlgHom hb)).comp (PowerSeries.substAlgHom ha) = PowerSeries.substAlgHom ⋯