Exploring IronPython using dir() doesn't always yield results.

Question

I'm playing around with IronPython and dir() does not always seem to work as I would expect. For instance:

import clr
clr.AddReference("IronPython")
clr.AddReference("Microsoft.Scripting")
from IronPython.Hosting import Python
py = Python.CreateEngine()
print dir(py.Operations)

Returns:

Traceback (most recent call last):
TypeError: __dir__() takes exactly 1 argument (0 given)

Ideas? Or is this some sort of bug?