Actually they optimized the hashmap, and it turned out a side effect of the optimization was insertion order. First implemented in pypy, then ported to cpython

Actually they optimized the hashmap, and it turned out a side effect of the optimization was insertion order. First implemented in pypy, then ported to cpython 3.6. Talk by Raimond Hettinger about the new implementation with several other implementations: https://m.youtube.com/watch?v=p33CVV29OG8# https://m.youtube.com/watch?v=p33CVV29OG8#