The Mater levels for Doom 2 are usually distributed as 20 separate WAD files.
This python script combines them into one single WAD.
This script needs only the omgifol library. It can be installed with pip, like this:
pip install omgifol
Just put glue_wads.py in the same directory as the 20 separate WAD files and do:
python glue_wads.py
The result will be saved in a file called doom_master_levels.wad