That was the first thing I checked, and it looks like they’re using some existing python package to parse docx files. I wonder if they contributed to it or vetted it strongly
They used Mammoth for docx (Word) [1][2] Python-pptx for ppt (PowerPoint) [3][4] and Pandas for XSLX (Excel) [5]
[1] https://github.com/microsoft/markitdown/blob/70ab149ff1657c3... [2] https://pypi.org/project/mammoth/ [3] https://github.com/microsoft/markitdown/blob/70ab149ff1657c3... [4] https://pypi.org/project/python-pptx/ [5] https://github.com/microsoft/markitdown/blob/70ab149ff1657c3...