proposition: Lemma I_unic : forall i1 i2 : Initial, Iso (Initial_ob i1) (Initial_ob i2).
proof: Proof. intros i1 i2. apply (Build_Iso (Iso_mor:=MorI i1 (Initial_ob i2)) (Inv_iso:=MorI i2 (Initial_ob i1))); unfold AreIsos in |- *; unfold RIso_law in |- *; split. apply (UniqueI (i:=i2) (b:=Initial_ob i2)). apply (UniqueI (i:=i1) (b:=Initial_ob i1)). Defined.
imports: Dual