errata upd. ch12
errata upd. ch12

chongyangma/python-machine-learning-book,chongyangma/python-machine-learning-book,rasbt/python-machine-learning-book,xdnian/pyml,rasbt/python-machine-learning-book,1iyiwei/pyml,xdnian/pyml,1iyiwei/pyml