How to check a PyObject for None in C#?

How to check an object returned from Python against None?

I can't find a good way to do it. This is my workaround which is very unsatisfying. 

```csharp
                var type = pyobj.__class__.ToString();
                if (type== "<class 'NoneType'>")
                    return null;
```

A simple `pyobj.IsNone` would be cool.  What am I missing?