code: def partition_key(self) -> CharStateKey:
      return CharStateKey(
          token_ix=self.token_ix,
          anno_ix=self.anno_ix,
      )
  
imports: import itertools
  import os
  import re
  from string import Template
  from typing import Any, Callable, Dict, List, NamedTuple, Optional, Tuple
  from tokenizers import Encoding, Tokenizer
label_desc: Use image node_id 4 for calling the CharState obj's underlying member method code with example usage: obj.partition_key() and returns: CharStateKey