<< KnotTheory`

KnotSignature[K=Knot[7,4]]

KnotSignature[PD[K]]

KnotSignature[Mirror[PD[K]]]

kikh=Expand[q+q^3+2t q^3+(q^5+2q^7)t^2+(q^7+q^9)t^3+(2q^9+q^11)t^4+2q^13t^5+q^13t^6+q^17t^7]

Kh[Knot[7,4]][q,t]

kikh /. t->-1/q^4