@hayd's I think the flaw with your approach is that if the user passes an incorrect keyword argument, no error is raised.  It seems to me we would want to raise a type error in such an event.

@jtratner The following experiment works for me:
```
>>> if np.ndarray([1,2]) is None:
...     print 'None'
... else:
...     print 'Not None'
... 
Not None
```