[R] Are there any open-source implementations of Document Understanding pipelines?

I have worked on several [Document Understanding](https://github.com/tstanislawek/awesome-document-understanding) (DU) projects for my company during the last year. We've mainly used UiPath and Google's DocumentAI.

Even though I know how these models theoretically work, I'd like to study the code behind them. I want to learn how exactly they combine OCR, NLP and Computer Vision to achieve their tasks instead of treating them like black boxes.

However, to my surprise, I've failed to find an open-source implementation of a DU model so …

document understanding machinelearning pipelines understanding