``__abstractmethods__`` is wrongly suggested for ``list``

When I type `list.__`, `__abstractmethods__` appears in the list of proposals. But when I tried to access this attribute, an AttributeError was raised. A screenshot is attached to make this clear.

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- Bitbucket: https://bitbucket.org/bobf/bpython/issue/97
- Originally Reported By: [Simon Liedtke](http://bitbucket.org/derdon)
- Originally Created At: 2010-01-24T13:22:52.291
