code: def get_diff_str(self, element, length):
          '''get_diff_str
  
          High-level api: Produce a string that indicates the difference between
          two models.
  
          Parameters
          ----------
  
          element : `Element`
              A node in model tree.
  
          length : `int`
              String length that has been consumed.
  
          Returns
          -------
  
          str
              A string that indicates the difference between two models.
          '''
  
          spaces = ' '*(self.get_width(element) - length)
          return spaces + element.get('diff'f get_diff_str(self, element, length):
          '''get_diff_str
  
          High-level api: Produce a string that indicates the difference between
          two models.
  
          Parameters
          ----------
  
          element : `Element`
              A node in model tree.
  
          length : `int`
              String length that has been consumed.
  
          Returns
          -------
  
          str
              A string that indicates the difference between two models.
          '''
  
          spaces = ' '*(self.get_width(element) - length)
          return spaces + element.get('diff')
docs: get_diff_str
  
          High-level api: Produce a string that indicates the difference between
          two models.
  
          Parameters
          ----------
  
          element : `Element`
              A node in model tree.
  
          length : `int`
              String length that has been consumed.
  
          Returns
          -------
  
          str
              A string that indicates the difference between two models.