class_docstr: The average stream CPU usage metric.
  This plugin metric works only at eval time.
  
  After the entire evaluation stream, this metric emits
  the average CPU usage on all experiences.
class_docstr_tok: ["The","average","stream","CPU","usage","metric",".","This","plugin","metric","works","only","at","eval","time",".","After","the","entire","evaluation","stream",",","this","metric","emits","the","average","CPU","usage","on","all","experiences","."]
code: def before_eval(self, strategy):
      super().before_eval(strategy)
      self.update(strategy)
  
imports: import os
  import warnings
  from typing import Optional, List
  from psutil import Process
  from avalanche.evaluation import Metric, PluginMetric, GenericPluginMetric
  from avalanche.evaluation.metrics import Mean
label_desc: Use image node_id 2 for calling the StreamCPUUsage obj's underlying member method code with example usage: obj.before_eval(strategy) without return types