I passed post_transform_stats via custom_config and tried to get artifacts like below in run_fn,
def run_fn(fn_args: FnArgs):
    """Callback function for Trainer component"""
    logging.info(fn_args.custom_config['tft_post_stats'])
    logging.info(fn_args.custom_config['tft_post_stats'].get())
    ...

and I couldn’t get any artifacts.
[2022-01-27 05:43:40,613][root][INFO] - Channel(
    type_name: ExampleStatistics
    artifacts: []
    additional_properties: {}
    additional_custom_properties: {}
)
[2022-01-27 05:43:40,613][root][INFO] - []

Maybe that’s because I tried to pass Channel via execution property.
I think I should try another ways. (mlmd or some other way)
But thanks for your reply! @Robert_Crowe