Fire can't find custom `__str__` of `~datasets.Dataset` from HuggingFace

[nerdai]

Hi,

I am using fire on a main function that returns a ~datasets.Dataset object. When running from cli, I get the help screen for ~datasets.Dataset rather than the __str__ implementation (likely inherited from a parent class -- haven't looked).

Reproducible example

from datasets import Dataset
import fire

def main():
    # Create a simple dataset
    dataset = Dataset.from_dict({"a": [1, 2, 3], "b": [4, 5, 6]})
    return dataset

if __name__ == "__main__":
    fire.Fire(main)
    
    # This works but I feel shouldn't be necessary:
    # def custom_serializer(obj: object) -> str:
    #     if hasattr(obj, "__str__"):
    #         return str(obj)
    #     else:
    #         return ""
    # fire.Fire(main, serialize=custom_serializer)

[dbieber]

Thanks for reporting. Agreed it would be better behavior for it to call __str__ than to show help.

The reason this happens is: HasCustomStr(dataset) == False

python-fire/fire/value_types.py

Line 58 in 51974c6

def HasCustomStr(component):

I think (haven't double checked) this is because Dataset overrides __repr__ but not __str__.

Related: #446