code: def handle_sys_utt(
      self, message: Message, prefix_stripped_text: str
  ) -> Optional[Dict[str, Metric]]:
      return self.handle_message_helper(prefix_stripped_text)
  
imports: from parlai.core.message import Message
  from parlai.core.metrics import Metric, AverageMetric, normalize_answer, BleuMetric, SumMetric
  from parlai.core.tod.tod_core import STANDARD_API_NAME_SLOT, STANDARD_REQUIRED_KEY, STANDARD_OPTIONAL_KEY, STANDARD_API_SCHEMAS
  from typing import Dict, List, Optional, Tuple
  from parlai.core.tod.world_metrics_handlers import TodMetricsHandler, register_metrics_handler, _ApiCallGoalInteractionHelper, goals_hit_helper
label_desc: Use image node_id 2 for calling the SystemUttSelfBleu3MetricHandler obj's underlying member method code with example usage: obj.handle_sys_utt(message, prefix_stripped_text) and returns: self