It's quite exciting how far we've come from the modern exposition of world models by David Ha and Jürgen Schmidhuber in 2018 https://worldmodels.github.io/
I don't think this is bad, if you know Python then most of the code will be fine for you. I think you're probably referring to pm_reduce_collapse, but while it looks daunting at first, it really isn't when you consider the alternatives, I'd be curious on how you'd improve it short of creating a DSL.
One anecdote in the same vein, a couple of months ago, I wanted to parse systemd-networkd INI files in Python and the python built-in ConfigParser [0] and pytest's iniconfig parser [1] couldn't handle multiple sections with the same name so I ended up writing 2 parsers, one using a ParserCombinator library and one by hand and ended up using the latter given it was much simpler to understand and I didn't have to introduce an extra dependency.
Admittedly, INI is quite a simple format, hence I mention this as an anecdote.
As a project gets larger the cost of owning a dependency directly begins to outweigh the impedance mismatch between 3rd party software & software customized to your project.
I've got 10 full time senior engineers on a project heading in to its 15th year. We rewrite even extremely low level code like std::vector or malloc to make sure it matches our requirements.
I have written parsers using parser combinators in Haskell and Clojure. I find that ML-like (Haskell, OCaml, StandardML) languages generally are great at writing parsers, even hand-written ones in it is a superior experience.
In this case, this was a project at $EMPLOYER in an existing codebase with colleagues who have never seen Haskell code, using Haskell would've been a major error in judgement.
I have used systemd services before to do this to run an application, I had a user created specifically for the application, and I defined the capabilities the application needed via CapabilityBoundingSet and AmbientCapabilities [0] and I used a lot of stuff from [1] to restrict the application e.g. the sandboxing facilities, restricting the allowed syscalls [2], ...etc. systemd also comes with a useful command systemd analyze security [3]
10 years ago I've implemented SCAMP (a gossip protocol) in Clojure, you might find it interesting, the implementation is quite small https://github.com/cipherself/gossip
