DISC: Validating internal docstring presence, completeness and style
We currently have guidelines/checks for docstrings https://pandas.pydata.org/docs/development/contributing_docstring.html  for the api facing methods/functions following the numpydoc docstring guide https://numpydoc.readthedocs.io/en/latest/format.html. since we also use sphinx for building the on-line documentation.

Many of our internal functions don't have docstrings and this could be a barrier to new contributions. For the more complex/undocumented internals, I am concerned that this may also affect the sustainability of the project if only a handful of contributors can grok the code.

The pandas docstring guidelines could be considered too heavyweight for internal functions and therefore may be factor in the incomplete coverage of docstrings for internal functions.