code: def __init__(self, data, vocab, y_assm):
      self.data = data
      self.vocab = vocab
      self.y_assm = y_assm
  
imports: import pickle
  import os
  import random
  import torch
  import numpy
  from torch.utils.data import Dataset, DataLoader
  from .mol_tree import MolTree
  from .jtnn_enc import JTNNEncoder
  from .mpn import MPN
  from .jtmpn import JTMPN
  from .vocab import Vocab
label_desc: Use image node_id 1 to create a new PairTreeDataset object from inherited base classes: Dataset with example: obj = PairTreeDataset(data, vocab, y_assm)