code: def calcu_used_tokens(self):
      tokens = 0
      for req in self.reqs:
          tokens += req.input_len + len(req.output_ids)
      return tokens
  
imports: from typing import Dict, List, Tuple
  from .sampling_params import SamplingParams
label_desc: Use image node_id 4 for calling the Batch obj's underlying member method code with example usage: obj.calcu_used_tokens() and returns: tokens