code: def __init__(self, data_path="./data/"):
      super(MultiBodyTestDataset, self).__init__(
          data_path + "n_body_test.npz"
      )
      self.test_traj = self.zipfile["test_traj"]
      self.first_frame = torch.from_numpy(self.zipfile["first_frame"])
  
imports: import copy
  import os
  import dgl
  import networkx
  import numpy
  import torch
  from torch.utils.data import DataLoader, Dataset
label_desc: Use image node_id 1 to create a new MultiBodyTestDataset object from inherited base classes: MultiBodyDataset with example: obj = MultiBodyTestDataset(data_path)