Acknowledgements
I was motivated to write this extension because I have found the literalinclude directive and pyobject option to be extremely useful when using Sphinx to write documentation for Python packages. I'm now using Zensical for most of my new projects, and wanted a similar feature.
The snippets extension comes close to meeting my needs, but I didn't want to add snippet markers to my source code.
However, I found this extension to be a useful reference for understanding how Python-Markdown preprocessors actually work.
It also provides many features that are well beyond the scope of includepy.
The mkdocs_graphviz extension inspired me to allow the user to adjust the extension priority, in case the default value happens to cause issues with other extensions.