GAP 4.8.9 installation with standard packages -- copy to your CoCalc project to get it
LoadPackage( "GradedRingForHomalg" ); Qxy := HomalgFieldOfRationalsInDefaultCAS( ) * "x,y"; S := GradedRing( Qxy ); wmat := HomalgMatrix( "[ \ x, -y\ ]", 1, 2, Qxy ); LoadPackage( "GradedModules" ); wmor := GradedMap( wmat, "free", [1,1], "left", S ); W := Cokernel( wmor ); W2 := UnderlyingObject(SubmoduleGeneratedByHomogeneousPart(2,S^0)); W3 := UnderlyingObject(SubmoduleGeneratedByHomogeneousPart(3,S^0)); W_neg := UnderlyingObject(SubmoduleGeneratedByHomogeneousPart(-2,S^4));