[Usage] TEST.EVAL_PERIOD doesn't seem to properly working

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Hi I currently use TEST.EVAL_PERIOD config for online evaluation and I put it in my command line (e.g, pods_train --num-gpus 8 TEST.EVAL_PERIOD 50). But what I found was it doesn't work and it works when I change the config file to TEST=dict(EVAL_PERIOD=50). Do you know why this problem happens? Im worriying that this phenomenon can make me unreliable in my argument setting.
Thanks