Missing %s docstring Missing module docstring Missing class docstring ...
Used when a module, function, class or method has no docstring. Some special methods like __init__() don't require a docstring and for those, this message is not raised if they have no docstring.
This message belongs to the basic checker.
Documentation Strings (called "docstrings") help you understand the intention of a module, function, class or method.
The chances that you will remember what each part of your code does is slim. Using docstrings will save you time and troubleshooting. Even the most descriptive function name (i.e. create_effective_rate_history()) will need a guide to its parameters.
Docstrings are helpful when using autodoc options in programs like Sphinx, so you, as the programmer, only have to describe a thing once.