1. There was a bug in the cross validator module from HW 3. In the docstring of cross_validator._get_xy_traincv() I had switched the usage of the "cv set" and the "training set." The correct docstring reads:
Returns slices of X and Y used for training and cv.  The cv
set should be e.g.:  X[istart: istop, :], and the training set should
be everything else.


The updated unit tests are here