Importing a parametric type sometimes causes a very weird error
Try to compile that file in that branch uncommenting that line:
https://github.com/KOLANICH/kaitai_struct_formats/blob/mdt/scientific/nt_mdt/nt_mdt.ksy#L14


https://github.com/KOLANICH/kaitai_struct_formats/blob/mdt/scientific/nt_mdt/nt_mdt_pal.ksy compiles and works fine