How to use the gphoto2.gp_widget_set_value function in gphoto2

# open camera connection
    camera = gp.check_result(gp.gp_camera_new())
    gp.check_result(gp.gp_camera_init(camera))
    # get configuration tree
    config = gp.check_result(gp.gp_camera_get_config(camera))
    # find the capture target config item
    capture_target = gp.check_result(
        gp.gp_widget_get_child_by_name(config, 'capturetarget'))
    # check value in range
    count = gp.check_result(gp.gp_widget_count_choices(capture_target))
    if value < 0 or value >= count:
        print('Parameter out of range')
        return 1
    # set value
    value = gp.check_result(gp.gp_widget_get_choice(capture_target, value))
    gp.check_result(gp.gp_widget_set_value(capture_target, value))
    # set config
    gp.check_result(gp.gp_camera_set_config(camera, config))
    # clean up
    gp.check_result(gp.gp_camera_exit(camera))
    return 0

OK, image_format = gp.gp_widget_get_child_by_name(config, 'imageformat')
    if OK >= gp.GP_OK:
        # get current setting
        value = gp.check_result(gp.gp_widget_get_value(image_format))
        # make sure it's not raw
        if 'raw' in value.lower():
            app.logger.debug('Cannot preview raw images')
            return 1
    # find the capture size class config item
    # need to set this on my Canon 350d to get preview to work at all
    OK, capture_size_class = gp.gp_widget_get_child_by_name(
        config, 'capturesizeclass')
    if OK >= gp.GP_OK:
        # set value
        value = gp.check_result(gp.gp_widget_get_choice(capture_size_class, 2))
        gp.check_result(gp.gp_widget_set_value(capture_size_class, value))
        # set config
        gp.check_result(gp.gp_camera_set_config(camera, config))
    # capture preview image (not saved to camera memory card)
    app.logger.debug('Capturing preview image')
    camera_file = gp.check_result(gp.gp_camera_capture_preview(camera))
    file_data = gp.check_result(gp.gp_file_get_data_and_size(camera_file))
    # display image
    data = memoryview(file_data)
    app.logger.debug(type(data), len(data))
    app.logger.debug(data[:10].tolist())
    fileName = os.path.join(PI_PREVIEW_DIR, PI_PREVIEW_FILE)
    if os.path.exists(fileName):
        os.remove(fileName)
    Image.open(io.BytesIO(file_data)).save(fileName, "JPEG")
    return 0

def set_datetime(config):
            OK, date_config = gp.gp_widget_get_child_by_name(config, 'datetime')
            if OK >= gp.GP_OK:
                widget_type = gp.check_result(gp.gp_widget_get_type(date_config))
                if widget_type == gp.GP_WIDGET_DATE:
                    now = int(time.time())
                    gp.check_result(gp.gp_widget_set_value(date_config, now))
                else:
                    now = time.strftime('%Y-%m-%d %H:%M:%S')
                    gp.check_result(gp.gp_widget_set_value(date_config, now))
                return True
            return False

def set_datetime(config):
            OK, date_config = gp.gp_widget_get_child_by_name(config, 'datetime')
            if OK >= gp.GP_OK:
                widget_type = gp.check_result(gp.gp_widget_get_type(date_config))
                if widget_type == gp.GP_WIDGET_DATE:
                    now = int(time.time())
                    gp.check_result(gp.gp_widget_set_value(date_config, now))
                else:
                    now = time.strftime('%Y-%m-%d %H:%M:%S')
                    gp.check_result(gp.gp_widget_set_value(date_config, now))
                return True
            return False

OK, image_format = gp.gp_widget_get_child_by_name(config, 'imageformat')
    if OK >= gp.GP_OK:
        # get current setting
        value = gp.check_result(gp.gp_widget_get_value(image_format))
        # make sure it's not raw
        if 'raw' in value.lower():
            app.logger.debug('Cannot preview raw images')
            return 1
    # find the capture size class config item
    # need to set this on my Canon 350d to get preview to work at all
    OK, capture_size_class = gp.gp_widget_get_child_by_name(
        config, 'capturesizeclass')
    if OK >= gp.GP_OK:
        # set value
        value = gp.check_result(gp.gp_widget_get_choice(capture_size_class, 2))
        gp.check_result(gp.gp_widget_set_value(capture_size_class, value))
        # set config
        gp.check_result(gp.gp_camera_set_config(camera, config))
    # capture preview image (not saved to camera memory card)
    app.logger.debug('Capturing preview image')
    camera_file = gp.check_result(gp.gp_camera_capture_preview(camera))
    file_data = gp.check_result(gp.gp_file_get_data_and_size(camera_file))
    # display image
    data = memoryview(file_data)
    app.logger.debug(type(data), len(data))
    app.logger.debug(data[:10].tolist())
    fileName = os.path.join(PI_PREVIEW_DIR, PI_PREVIEW_FILE)
    if os.path.exists(fileName):
        os.remove(fileName)
    Image.open(io.BytesIO(file_data)).save(fileName, "JPEG")
    return 0