code: def event_type_set(self):
      type_set = set()
      for inst in self.insts:
          for event in inst["event_mentions"]:
              type_set.add(event["event_type"])
      return type_set
  
imports: import json, logging, pickle
  from mimetypes import knownfiles
  from unittest.mock import NonCallableMagicMock
  import torch
  from torch.utils.data import Dataset
  from collections import namedtuple
label_desc: Use image node_id 4 for calling the EEDataset obj's underlying member method code with example usage: obj.event_type_set() and returns: type_set