gap> arc:=[[1,2],[1,2]];;
gap> K:=ArcPresentationToKnottedOneComplex(arc);
Map of regular CW-complexes

gap> f:=RegularCWComplexComplement(K);
Testing contractibility...
79 out of 79 cells tested.
2 cell(s) will be barycentrically subdivided.
Map of regular CW-complexes