code: def get_tss(self):
          
          tss = 0
          for class_def in self.classes:
              if len(class_def) > 0:
                  yc = self.y[class_def]
                  css = yc - yc.mean()
                  css *= css
                  tss += sum(css)
          return tss
docs: Total sum of squares around class means
  
          Returns sum of squares over all class means