code: def next(self):
          
          if self.start + self.size > self.total_size:
              result = None
          else:
              result = Batch(self.start + self.size, self.size, self.total_size)
          return result
docs: Returns the next batch for the batched sequence or `None`, if
          this batch is already the last batch.
  
          :rtype: :class:`Batch` instance or `None`.