code: def add_special(self, sym):
      if sym not in self.sym2idx:
          self.idx2sym.append(sym)
          self.sym2idx[sym] = len(self.idx2sym) - 1
          setattr(
              self, "{}_idx".format(sym.strip("<>")), self.sym2idx[sym]
          )
  
imports: import contextlib
  import os
  from collections import Counter
  from collections import OrderedDict
  import torch
  from src.utils.distributed import sync_workers
label_desc: Use image node_id 9 for calling the Vocab obj's underlying member method code with example usage: obj.add_special(sym) without return types