code: def rdlevenshtein_norm(source, target):
      
  
      # Compute restricted Damerau-Levenshtein distance using helper function.
      # The max is always just the length of the longer string, so this is used
      # to normalize result before returning it
      distance = _levenshtein_compute(source, target, True)
      return float(distance) / max(len(source), len(target))
docs: Calculates the normalized restricted Damerau-Levenshtein distance
      (a.k.a. the normalized optimal string alignment distance) between two
      string arguments. The result will be a float in the range [0.0, 1.0], with
      1.0 signifying the maximum distance between strings with these lengths