GAP 4.8.9 installation with standard packages -- copy to your CoCalc project to get it
gap> START_TEST("HAP library"); gap> K:=PureCubicalKnot(3,1); prime knot 1 with 3 crossings gap> L:=KnotReflection(K); Reflected( prime knot 1 with 3 crossings ) gap> S:=KnotSum(K,L); prime knot 1 with 3 crossings + Reflected( prime knot 1 with 3 crossings ) gap> DisplayArcPresentation(S); gap> STOP_TEST( "tst.tst", 1000 );