def _labelToCategoryNumber(self, label):
if label not in self.saved_categories:<EOL><INDENT>self.saved_categories.append(label)<EOL><DEDENT>return pow(<NUM_LIT:2>, self.saved_categories.index(label))<EOL>
Since the KNN Classifier stores categories as numbers, we must store each
label as a number. This method converts from a label to a unique number.
Each label is assigned a unique bit so multiple labels may be assigned to
a single record.