code: def _every(times, step_size, index):
          
          current = index * step_size
          step = current // times * times
          reached = current >= step
          overshot = current >= step + step_size
          return current and reached and not overshot
docs: Given a loop over batches of an iterable and an operation that should
          be performed every few elements. Determine whether the operation should
          be called for the current index.