code: def get_class_set(labels):
      """Get the class set.
      Input: labels [l, [c1, c2, ..]]
      Output：the labeled class set dict_keys([k1, k2, ..])
      """
      mydict = {}
      for y in labels:
          for label in y:
              mydict[int(label)] = 1
      return mydict.keys()
  
imports: from collections import defaultdict
  import numpy
  import torch
label_desc: Use image node_id 2 for calling a global function with example usage: get_class_set(labels) and returns: mydict