code: def _fetch(self, index: int) -> Tuple[TimeSeries, slice]:
      scope_id, start, length = self.windows[index]
      window = slice(start, start + length)
      return self.corpus[scope_id], window
  
file_path: gluonts/src/gluonts/nursery/daf/tslib/dataset/windows.py
imports: from __future__ import annotations
  from typing import Optional, List, Tuple, Any
  from itertools import repeat
  from torch.utils.data import Dataset
  from tqdm import tqdm
  import numpy
  from .timeseries import TimeSeries, TimeSeriesCorpus
label_desc: Use image node_id 3 for calling the WindowsDataset obj's underlying member method code with example usage: obj._fetch(index) and returns: self,  window