input: def cyclic_shift_encode(s: str):
      """
      Encodes the input string by rotating groups of three characters.
      """
      # Divide the string into three-character segments.
      groups = [s[(3 * i):min((3 * i + 3), len(s))] for i in range((len(s) + 2) // 3)]
      # Rotate characters within each group, unless the group size is less than three.
      groups = [(group[1:] + group[0]) if len(group) == 3 else group for group in groups]
      return "".join(groups)
  
  
  def cyclic_shift_decode(s: str):
      """
      Decodes a string that was encoded using the cyclic_shift_encode function.
      """
output:     # Divide the string into three-character segments.
      groups = [s[(3 * i):min((3 * i + 3), len(s))] for i in range((len(s) + 2) // 3)]
      # Rotate characters back within each group, unless the group size is less than three.
      groups = [(group[-1] + group[:-1]) if len(group) == 3 else group for group in groups]
      return "".join(groups)