GAP 4.8.9 installation with standard packages -- copy to your CoCalc project to get it
LoadPackage( "Modules" ); ZZ := HomalgRingOfIntegers( ); I := RightSubmodule( "4", ZZ ); J := Subobject( HomalgMatrix( "[ 6 ]", 1, 1, ZZ ), UnderlyingObject( I ) );