Document DataFrame._constructor_sliced-like property in the public API?
Can we document something like `DataFrame._constructor_sliced` as the public way to say that slicing a column from a pandas.DataFrame will return a pandas.Series object?

Projects like Dask would like to work with any concrete DataFrame library (cudf being the second major dataframe implementation). Right now we resort to things like `type(dask.dataframe.DataFrame._meta.iloc[:, 0])` to get the concrete type of a slice. But that's fragile (e.g. a DataFrame with no columns).

I'm not sure how useful this would be to users, so using an underscore-prefixed name may be reasonable.