code: def unk_index(self):
      if self.unk is not None:
          return self.tokens.index(self.unk)
      else:
          raise AttributeError
  
file_path: underthesea/underthesea/utils/sp_embedding.py
imports: import torch
label_desc: Use image node_id 5 for calling the Embedding obj's underlying member method code with example usage: obj.unk_index() and returns: self