In the scripts, the variable chains is used all over the place. Unfortunately, chains is also exported by MCMCChains, which can cause issues like

julia> chains = sample(model(a, b), NUTS(0.65), 1000)
ERROR: invalid redefinition of constant chains

Thanks to David Widmann for figuring this out (TuringLang/Turing.jl#1529).

To solve this issue, and avoid problems in the future for us and for users, we would be better of renaming the variables to chn or chns or something.