strange bug using jupyter notebook

hey - no idea if this is a bug in toolz or in jupyter notebook, figured I would post here to help try to diagnose a pretty strange bug.

I'm using memoize as a decorator on a function that takes no arguments. I have used this approach many times in many contexts as a convenient local memory cache. The strange thing is, this raises an exception when I call the code from a jupyter notebook, but not from an ipython console and not in a stand-alone python script.

The exception I'm getting:

/home/jstrong/src/envs/vc/local/lib/python2.7/site-packages/toolz/functoolz.pyc in memof(*args, **kwargs)
    402             return cache[k]
    403         except TypeError:
--> 404             raise TypeError("Arguments to memoized function must be hashable")
    405         except KeyError:
    406             cache[k] = result = func(*args, **kwargs)

TypeError: Arguments to memoized function must be hashable

Does anything come to mind to explain how this bug could only arise when the code is called from a jupyter notebook?

First reproduce the zero-argument memoize call in a Jupyter notebook, an IPython console, and a standalone Python script. Then inspect toolz/functoolz.pyc around the memoized-function path at line 404 and determine why the notebook context produces an unhashable key; done means the cause is identified and the behavior is covered by a regression test.