∀ {R : Type u} {A : Type v} [inst : CommSemiring R] [inst_1 : AddCommMonoid A] [inst_2 : Module R A]
  [inst_3 : Coalgebra R A],
  LinearMap.rTensor A CoalgebraStruct.comul ∘ₗ CoalgebraStruct.comul =
    ↑(TensorProduct.assoc R A A A).symm ∘ₗ LinearMap.lTensor A CoalgebraStruct.comul ∘ₗ CoalgebraStruct.comul