code: def _F_measure(self, alpha, TP, FP, FN, return_num_den=False):
          
          num = np.float64(TP)
          den = np.float64(alpha * (TP + FP) + (1 - alpha) * (TP + FN))
          with np.errstate(divide='ignore', invalid='ignore'):
              F_measure = num/den
          #F_measure = num/den
  
          if return_num_den:
              return F_measure, num, den
          else:
              return F_measure
docs: Calculate the weighted F-measure