Testing for membership in an ndarray segfaults: ``` In [1]: pd.NA in np.array(["a"], dtype=object) Segmentation fault (core dumped) ``` Now, this might be something that needs to be fixed in numpy, as for plain lists it "works": ``` In [3]: pd.NA in ['a'] ... TypeError: boolean value of NA is ambiguous ``` but numpy might not expect an error instead of True/False.