Outdated DataFrame.partition_by docstring for as_dict behavior

[d-laub]

Description

Documentation for DataFrame.partition_by v1.0.0 does not reflect changes from #16793

as_dict
Return a dictionary instead of a list. The dictionary keys are tuples of the distinct group values that identify each group. If a single string was passed to by, the keys are a single value instead of a tuple.

This conflicts with the runtime behavior where the dictionary keys are tuples when by is a string.

>>> df = pl.DataFrame({"foo": ["a", "a", "b"], "bar": [1, 2, 3]})
>>> print(df.partition_by("foo", as_dict=True).keys())
dict_keys([('a',), ('b',)])

Link

https://docs.pola.rs/api/python/stable/reference/dataframe/api/polars.DataFrame.partition_by.html#polars.DataFrame.partition_byddd

[nameexhaustion]

Fixed by #17394