@Nullable
    private static String getPrintableName(@Nullable PyType type) {
      if (type instanceof PyUnionType) {
        return StreamEx
          .of(((PyUnionType)type).getMembers())
          .map(Visitor::getPrintableName)
          .joining(" or ");
      }
      else if (type != null) {
        return type.getName();
      }
      else {
        return PyNames.UNKNOWN_TYPE;
      }
    }
@Nullable
    private static String getPrintableName(@Nullable PyType type)