class_docstr: Training Dataset class.
  Parameters
  ----------
  triples: The triples used for training the model
  num_ent: Number of entities in the knowledge graph
  lbl_smooth: Label smoothing
  
  Returns
  -------
  A training Dataset class instance used by DataLoader
code: def __init__(self, triples, num_ent, lbl_smooth):
      self.triples = triples
      self.num_ent = num_ent
      self.lbl_smooth = lbl_smooth
      self.entities = np.arange(self.num_ent, dtype=np.int32)
  
imports: from collections import defaultdict
  import dgl
  import numpy
  import torch
  from ordered_set import OrderedSet
  from torch.utils.data import DataLoader, Dataset
label_desc: Use image node_id 1 to create a new TrainDataset object from inherited base classes: Dataset with example: obj = TrainDataset(triples, num_ent, lbl_smooth)