code: def __len__(self):
      return self.roll_start_idxes.size
  
file_path: analytics-zoo/pyzoo/zoo/chronos/data/utils/roll_dataset.py
imports: import numpy
  from torch.utils.data import Dataset
  import torch
  from zoo.chronos.data.utils.utils import _check_cols_no_na, _to_list
label_desc: Use image node_id 2 for calling the RollDataset obj's underlying member method code with example usage: obj.__len__() and returns: self