code: def aggregate(self, values):
      mean = values.mean().item()
      logger.info(f"{self.key}: {mean}")
      self.values.append(mean)
  
imports: import logging
  from collections import deque
  from typing import Any, Callable, Deque, Dict, List, Optional
  import numpy
  import torch
  from reagent.core.tensorboardX import SummaryWriterContext
  from reagent.core.tracker import Aggregator
label_desc: Use image node_id 2 for calling the MeanAggregator obj's underlying member method code with example usage: obj.aggregate(values) without return types