Currently, dimlvlmap with identity affine map will be treated as empty affine map. But the new syntax would treat it as an actual identity affine map such as {d0} -> {d0}. This mismatch could raise an error when we are comparing sparse encodings.
{Var,DimLvlExpr,DimSpec,LvlSpec,DimLvlMap}::str
DimLvlMapParser