Module K := K'.
Arguments unsquash_inj [k1 k2] _.
Arguments unsquash_approx [k n Fp] _.

Lemma approx_spec': forall n p k,
((fun (p: knot -> Prop) ko => p (@fst _ unit ko)) oo app_pred) (approx n p) k =
if (le_gt_dec n (level (fst k))) then False else
((fun (p: knot -> Prop) ko => p (@fst _ unit ko)) oo app_pred) p k.