fact: Definition inO_isequiv_to_O (T:Type) : IsEquiv (to O T) -> In O T := fun _ => inO_equiv_inO (O T) (to O T)^-1.
imports: HoTT.Basics HoTT.Types Equiv.BiInv Extensions HProp HFiber NullHomotopy Limits.Pullback PathAny Colimits.Pushout