How to use Aravis Python?

  1. How to call these 2 functions?
camera.set_gain_auto()
camera.set_exposure_time_auto()

Both of these 2 functions require 2 parameters:

xception has occurred: TypeError
Aravis.Camera.set_gain_auto() takes exactly 2 arguments (1 given)
  File "....../arv-camera-test.py", line 34, in <module>
    camera.set_gain_auto()
  1. Why there is ALWAYS such an ERROR while writing into USB3Vision camera?
Exception has occurred: GError
arv-device-error-quark: USB3Vision write_memory error (access-denied) (5)
  File "....../arv-camera-test.py", line 31, in <module>
    camera.set_region (0,0,1440,1080)
  1. How to let Aravis automatically find multiple cameras?
    I mean camera2 = Aravis.Camera.new (None) ONLY finds the very FIRST camera, but NOT the other cameras.

For discovering multiple cameras:

Aravis.update_device_list()
devices = Aravis.get_n_devices()