It also runs pretty fast (even for a big library), because it doesn't parse the whole library before trying to display the contents.
Official link in GitHub
After reading the code, and testing some example sample XML files, it seems that the code is really self-documented, so there shouldn't be any issues regarding understanding the code. The comments are here for more general ideas about what the code does and what the data is, though.
Here's the description of some of 50e0806aeb hanangu