code: def lookup_index(self, index: int):
      if index not in self._id2token:
          raise ValueError(
              f"Index {index} is not present in the Vocabulary"
          )
  
      else:
          return self._id2token[index]
  
imports: from typing import Dict
label_desc: Use image node_id 7 for calling the Vocabulary obj's underlying member method code with example usage: obj.lookup_index(index) and returns: self