code: def __len__(self):
      return len(self.tokens) - self.idx
  
imports: import re
  from dataclasses import dataclass, InitVar, field
  from itertools import chain
  from typing import Any, Dict, List, Union, Optional, ClassVar
  import numpy
  from toolz import valfilter, valmap
label_desc: Use image node_id 5 for calling the TokenStream obj's underlying member method code with example usage: obj.__len__() and returns: unknown