API documentation should state return types

[fulldecent]

As an example, let's see the documentation for pandas.DataFrame.dtypes:

Documentation:

DataFrame.dtypes
Return the dtypes in this object.

https://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.dtypes.html

This documentation is insufficient to describe the function. Perhaps a better documentation would state something like:

DataFrame.dtypes

Return a series of dtypes in this object.
Return type is pandas.core.series.Series with elements of numpy.dtype.

And those two types should link to related to documentation if available.

[jreback]

sure there are doc strings that could use updating

[TomAugspurger]

This has been fixed.