code: def _groups_of(length, total_length):
      
      indices = tuple(range(0, total_length, length)) + (None, )
      return _pairwise(indices)
docs: Return an iterator of tuples for slicing, in 'length' chunks.
  
      Parameters
      ----------
      length : int
          Length of each chunk.
      total_length : int
          Length of the object we are slicing
  
      Returns
      -------
      iterable of tuples
          Values defining a slice range resulting in length 'length'.