That fixes the first problem in python 2. It should do:

self.matching_blocks = [Match._make(t) for t in non_adjacent]

in python 3 though, or it will return an already-exhausted map object if it is called again.

This leaves the problem of other code mutating the cached list (not realizing it is cached). I think it would make sense for these functions to just return a shallow copy of their cached list, but I have not thought that through much.