code: def _labelListToCategoryNumber(self, labelList):
      
      categoryNumber = 0
      for label in labelList:
        categoryNumber += self._labelToCategoryNumber(label)
      return categoryNumber
docs: This method takes a list of labels and returns a unique category number.
      This enables this class to store a list of categories for each point since
      the KNN classifier only stores a single number category for each record.