def accumulated_token_usage(self) -> TokenUsage:
        """Get the accumulated token usage, initializing it if it doesn't exist."""
        if not hasattr(self, '_accumulated_token_usage'):
            self._accumulated_token_usage = TokenUsage(
                model=self.model_name,
                prompt_tokens=0,
                completion_tokens=0,
                cache_read_tokens=0,
                cache_write_tokens=0,
                context_window=0,
                response_id='',
            )
        return self._accumulated_token_usage
Get the accumulated token usage, initializing it if it doesn't exist.
openhands/llm/metrics.py