old_contents: 
  def fragment(sequence, size=5):
      """
      Fragment a string sequence using a sliding window given by size
  
      :param sequence: String containing the sequence
      :param size: Size of the window
  
      :return: a fragment of the sequence with the given size
      """
      for i in range(len(sequence) - size + 1):
          yield sequence[i: i + size]
  
  
new_contents: 
  def fragment(sequence, size=5):
      """
      Fragment a string sequence using a sliding window given by size
  
      :param sequence: String containing the sequence
      :param size: Size of the window
  
      :return: a fragment of the sequence with the given size
      """
      if size > 0:
          for i in range(len(sequence) - size + 1):
              yield sequence[i: i + size]
  
subject: Handle sliding window with size 0