code: def __getitem__(self, key):
      if isinstance(key, str):
          if key in self.vocab_dict:
              return self.vocab_dict[key]
          else:
              return self.vocab_dict[self.unk_token]
      else:
          return self.vocab_lst[key]
  
file_path: dgl/examples/pytorch/transformer/dataset/fields.py
label_desc: Use image node_id 4 for calling the Vocab obj's underlying member method code with example usage: obj.__getitem__(key) and returns: self, self, self