@NotNull
    public <S> PsiToStubConversion<Psi, PsiStub, S> withCustomStub(@NotNull Function<@NotNull PsiStub, @Nullable S> stubGetter) {
      return new PsiToStubConversion<>(myElement, myStubGetter, psi -> {
        PsiStub stub = myStubGetter.apply(psi);
        return stub != null ? stubGetter.apply(stub) : null;
      });
    }
@NotNull
    public <S> PsiToStubConversion<Psi, PsiStub, S> withCustomStub(@NotNull Function<@NotNull PsiStub, @Nullable S> stubGetter)