Sorry if I came out a bit snippy out there. But yeah I assumed you meant python without numpy, etc.

A lot of the criticism I saw was because the core routines did not need to be packaged up. There were a lot of common data structures reimplemented, etc.

I don't think the model had many novel routines. It could be built just using industry standard and tested tools in python, R, Julia (if you really want speed) etc. But it reinvented the whole ecosystem in one big ball of C.

tbh, this should have been built on STAN or similar. There's so many variables and assumptions that the output is completely dominated by the parameters chosen. Seeing the distribution of outcomes instead of a point estimate would be actually useful.