Plotting A Graph On Axes But Getting No Results While Trying To Classify Image Based On Hog Features

I need to use boosted cascaded training to classify some images in scikit-learn. I want to classify according to HoG features. My code below is adapted from this example. This part

Solution 1:

I would have deleted this question but it occurred to me that another newbie at classification might have the same issue so I'm just answering the question.

The problem was because of a very silly mistake - my training array, labels, had no negatives, it consisted entirely of labels for only one class.