I have been told that you should not generate documentation from code, and there are probably several good reasons behind that guideline. However, for the specific purpose of documenting and testing the small-scale projects I have using Pythonista, I really prefer maintaining only the docstrings that are in the code, and then generating the markdown documentation for Github.
docgen is a single-file utility that is intended to be run from the Pythonista action menu. Check the README file for usage.
For "real-life" examples of the generated documentation, see the Scripter and Gestures docs.