code: def normalize_bit(A, B, bit, id2desc):
      
      Amax, Bmax = id2desc[A][-1], id2desc[B][-1]
      norm_factor = float(numpy.average([Amax, Bmax]))
      normalized = bit / norm_factor
      return normalized
docs: normalize the bit score:
      normalization factor = average max bit score for the two ORFs
      normalized = bit score / normalization factor