@attr.s
class A:
    a = attr.ib()
        
instance = A({(1, ): 1})
attr.asdict(instance)

produces:
TypeError: unhashable type: 'list'

when the retain_collection_types flag is set to false (the default). This can take a while to figure out, since the error is not the most descriptive (and the classes are not toy examples like this one).
I just thought it would be worth mentioning. In any case, thanks for this awesome library.