docs: def processes_with_env_psutil(env_name, env_value):
      """
      Find PIDs of processes having environment variable matching given one.
  
      Internally it uses `psutil` library.
  
      :param str env_name: name of environment variable to be found
      :param str env_value: environment variable value prefix
      :return: process identifiers (PIDs) of processes that have certain
               environment variable equal certain value
      :rtype: set
      """
      pids = set()
  
      for proc in psutil.process_iter():
          try:
              pinfo = proc.as_dict(attrs=['pid', 'environ'])
          except (psutil.NoSuchProcess, IOError):
              # can't do much if psutil is not able to get this process details
              pass
          else:
              penv = pinfo.get('environ')
              if penv and env_value in penv.get(env_name, ''):
                  pids.add(pinfo['pid'])
  
      return pids