The parameter getter can cause kernel crashes when a model's parameters cannot be parsed into arrays/matrices of f64 since the mappings use unwraps. This is annoying because it can happen e.g. by tapping TAB in a notebook on a model for auto-completion.

Quick fix: remove getter. If the method is called (and not used as getter), PyO3 will wrap the panic in an error which keeps the kernel alive.

Longer term: create a better way to retrieve parameters from a model.