code: def __init__(self, length, flag):
      self.length = length
      self.flag = flag
      self.shapes = np.random.random((length, 2))
  
imports: import bisect
  from unittest import TestCase
  from unittest.mock import patch
  import numpy
  from torch.utils.data import ConcatDataset, Dataset
  from mmdet.datasets.samplers import GroupMultiSourceSampler, MultiSourceSampler
label_desc: Use image node_id 1 to create a new DummyDataset object from inherited base classes: Dataset with example: obj = DummyDataset(length, flag)