source code for extracting a mapping of IP address to NAT (yes/no?) property
The problem of extracing the feature "is a particular IP address a NAT?" is non trivial unless you have a lot of traffic from all over the world to observer (such as google, fb.com etc) or ad-networks at your disposal or global netflow traffic.
However, here we start small and extend as we go: we take existing measurement data sets (such as RIPE Atlas) and collect the info that these measurements say about their NAT status of their IP address. This is of course by far not complete, but it is a start and can be seen as an initial attempt.
Note: since most residential IP addresses (and most corporate ones) are actually a NAT, hiding at least one internal IP address (think DSL/cable modems usually being a NAT), we should not be surprised to see lots of (IPv4) NAT addresses in the course of time.