code: def keys(self):
      return []
  
imports: import torch
  from torch_geometric.data import Data, Batch
  from torch_points3d.datasets.batch import SimpleBatch
  from torch_points3d.core.data_transform import MultiScaleTransform
  from torch_points3d.datasets.multiscale_data import MultiScaleBatch
label_desc: Use image node_id 2 for calling the MockDatasetConfig obj's underlying member method code with example usage: obj.keys() and returns: list