Draw the precision-recall curves in the multiclass case

def _draw_multiclass(self):
        """
        Draw the precision-recall curves in the multiclass case
        """
        # TODO: handle colors better with a mapping and user input
        if self.per_class:
            for cls in self.classes_:
                precision = self.precision_[cls]
                recall = self.recall_[cls]

                label = "PR for class {} (area={:0.2f})".format(cls, self.score_[cls])
                self._draw_pr_curve(recall, precision, label=label)

        if self.micro:
            precision = self.precision_[MICRO]
            recall = self.recall_[MICRO]
            self._draw_pr_curve(recall, precision)

        self._draw_ap_score(self.score_[MICRO])