code: def test_cpu_monitor():
      cpu_monitor = CPUMonitor()
      cpu_monitor.collect_metrics()
  
      assert isinstance(
          cpu_monitor.metrics["cpu_utilization_percentage"], list
      )
      assert isinstance(
          cpu_monitor.metrics["system_memory_usage_megabytes"], list
      )
  
      cpu_monitor.collect_metrics()
      aggregated_metrics = cpu_monitor.aggregate_metrics()
      assert isinstance(
          aggregated_metrics["cpu_utilization_percentage"], float
      )
      assert isinstance(
          aggregated_metrics["system_memory_usage_megabytes"], float
      )
  
      cpu_monitor.clear_metrics()
      assert cpu_monitor.metrics == {}
  
imports: from mlflow.system_metrics.metrics.cpu_monitor import CPUMonitor
  from mlflow.system_metrics.metrics.disk_monitor import DiskMonitor
  from mlflow.system_metrics.metrics.gpu_monitor import GPUMonitor
  from mlflow.system_metrics.metrics.network_monitor import NetworkMonitor
label_desc: Use image node_id 1 for calling a global function with example usage: test_cpu_monitor() without return types