Method finalize

runners/helpers/CountTokens.cpp:116–118

    return sb.as_cslice().str();
  }
  std::string finalize() override {
    return last_;
  }
  ton::tl_object_ptr<cocoon_api::tokensUsed> usage() override {
    auto prompt_tokens_adj = adjust_tokens(prompt_tokens_ - cached_tokens_, coef_, prompt_tokens_mult_);
    auto cached_tokens_adj = adjust_tokens(cached_tokens_, coef_, cached_tokens_mult_);