Regarding Claudiu's comment about `staticmethod(x)` or `classmethod(x)` not being callable, would it suffice to add a specific check of the form `(isinstance(x, (classmethod, staticmethod)) and _callable(x.__func__))`?

Separately, would it be better to include the check for `staticmethod` and `classmethod` objects (with an underlying callable) inside the `_callable` function? Not sure if this would break anything, but it seems like conceptually the issue is with the definition of a callable object, not the selection of mock type to use.