code: def clean_processes():
      for pid in list(GPUStatCollection.global_processes.keys()):
          if not psutil.pid_exists(pid):
              del GPUStatCollection.global_processes[pid]
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from __future__ import unicode_literals
  import json
  import platform
  import sys
  from datetime import datetime
  import psutil
  from ..gpu import pynvml
label_desc: Use image node_id 2 for calling the GPUStatCollection obj's underlying member method code with example usage: obj.clean_processes() without return types