Inconsistent output in documentation example: num_classes not displayed in ClassLabel output

[sergiopaniego]

In the documentation for ClassLabel, there is an example of usage with the following code:

from datasets import Features
features = Features({'label': ClassLabel(num_classes=3, names=['bad', 'ok', 'good'])})
features

which expects to output (as stated in the documentation):

{'label': ClassLabel(num_classes=3, names=['bad', 'ok', 'good'], id=None)}

but it generates the following

{'label': ClassLabel(names=['bad', 'ok', 'good'], id=None)}

If my understanding is correct, this happens because although num_classes is used during the init of the object, it is afterward ignored:

datasets/src/datasets/features/features.py

Line 975 in be5cff0

num_classes: InitVar[Optional[int]] = None # Pseudo-field: ignored by asdict/fields when converting to/from dict

I would like to work on this issue if this is something needed 😄