CPPI is a standard inteface definition for prop protectors. It is up to the individual prop protection scripts to implement it within their codebase.
The specification should tell you everything you need to know in order to implement or use the CPPI.
You can see an example implementation in UPS under /lua/ups/modules/sh/cppi.lua if that's what you're looking for, but it is specific to UPS's function set.