code: def sliding(self, size, step=1):
          
          return self._transform(transformations.sliding_t(_wrap, size, step))
docs: Groups elements in fixed size blocks by passing a sliding window over them.
  
          The last window has at least one element but may have less than size elements
  
          :param size: size of sliding window
          :param step: step size between windows
          :return: sequence of sliding windows