Definition knot_rel (k1 k2:knot) :=
    let (n,f) := unsquash k1 in
    let (n',f') := unsquash k2 in
    n = n' /\ KI.Rel predicate f f'.

Lemma unsquash_inj : forall k1 k2, unsquash k1 = unsquash k2 -> k1 = k2.