code: def levenshtein_norm(source, target):
      
  
      # Compute 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, False)
      return float(distance) / max(len(source), len(target))
docs: Calculates the normalized Levenshtein distance between two string
      arguments. The result will be a float in the range [0.0, 1.0], with 1.0
      signifying the biggest possible distance between strings with these lengths