public static DfReferenceType customObject(@NotNull TypeConstraint constraint,
                                             @NotNull DfaNullability nullability,
                                             @NotNull Mutability mutability,
                                             @Nullable SpecialField jvmSpecialField,
                                             @NotNull DfType sfType) {
    if (nullability == DfaNullability.NULL) {
      throw new IllegalArgumentException();
    }
    return new DfGenericObjectType(Set.of(), constraint, nullability, mutability, jvmSpecialField, sfType, false);
  }
public static DfReferenceType customObject(@NotNull TypeConstraint constraint,
                                             @NotNull DfaNullability nullability,
                                             @NotNull Mutability mutability,
                                             @Nullable SpecialField jvmSpecialField,
                                             @NotNull DfType sfType)