docs: def start_guest(userid):
      """ Power on the vm.
  
      Input parameters:
      :userid:            USERID of the guest, last 8 if length > 8
      """
      # Check the power state before starting guest.
      power_state_info = client.send_request('guest_get_power_state', userid)
      print("\nPower state is: %s." % power_state_info['output'])
  
      # start guest.
      guest_start_info = client.send_request('guest_start', userid)
  
      if guest_start_info['overallRC']:
          raise RuntimeError('Failed to start guest %s!\n%s' % 
                             (userid, guest_start_info))
      else:
          print("Succeeded to start guest %s!" % userid)
  
      # Check the power state after starting guest.
      power_state_info = client.send_request('guest_get_power_state', userid)
      print("Power state is: %s." % power_state_info['output'])
  
      if guest_start_info['overallRC']:
          print("Guest_start error: %s" % guest_start_info)