Looking around at some models, they seem to be like state machines to describe specific subsystems of different organisms.

The seem to be using a markup format called [SBML](https://synonym.caltech.edu/).

> Many software tools and databases support SBML directly. You don’t write in SBML yourself—your software does it for you.

So its likely that you aren't supposed to parse/write the SBML directly. The BioModels website also provides PNGs so you can look at the state machines visually.