Probably a typo: "mannie_service" vs "make_sentient" near Loc 660 in ebook.

[WraithGlade]

The code example in Listing 4 says "mannie_service" as the names of the two overloaded functions, but later elaborations of the example use "make_sentient" instead. This seems like a likely typo.

Also, I have no idea what "mannie_service" is supposed to mean.

[JLospinoso]

Thanks, @WraithGlade!