set COMMANDLINE_ARGS=--api getting error

I edit the window batch file with the line: set COMMANDLINE_ARGS=--api, so that I could use the plugin but doesn't work. How could I fix it?

Here is the result after I add the command line
Installing requirements for Web UI
Launching Web UI with arguments: --api
usage: launch.py [-h] [--config CONFIG] [--ckpt CKPT] [--ckpt-dir CKPT_DIR] [--gfpgan-dir GFPGAN_DIR]
[--gfpgan-model GFPGAN_MODEL] [--no-half] [--no-progressbar-hiding]
[--max-batch-count MAX_BATCH_COUNT] [--embeddings-dir EMBEDDINGS_DIR] [--allow-code] [--medvram]
[--lowvram] [--always-batch-cond-uncond] [--unload-gfpgan] [--precision {full,autocast}] [--share]
[--codeformer-models-path CODEFORMER_MODELS_PATH] [--gfpgan-models-path GFPGAN_MODELS_PATH]
[--esrgan-models-path ESRGAN_MODELS_PATH] [--bsrgan-models-path BSRGAN_MODELS_PATH]
[--realesrgan-models-path REALESRGAN_MODELS_PATH] [--scunet-models-path SCUNET_MODELS_PATH]
[--swinir-models-path SWINIR_MODELS_PATH] [--ldsr-models-path LDSR_MODELS_PATH] [--xformers]
[--force-enable-xformers] [--deepdanbooru] [--opt-split-attention] [--disable-opt-split-attention]
[--opt-split-attention-v1]
[--use-cpu {SD,GFPGAN,BSRGAN,ESRGAN,SCUNet,CodeFormer} [{SD,GFPGAN,BSRGAN,ESRGAN,SCUNet,CodeFormer} ...]]
[--listen] [--port PORT] [--show-negative-prompt] [--ui-config-file UI_CONFIG_FILE]
[--hide-ui-dir-config] [--ui-settings-file UI_SETTINGS_FILE] [--gradio-debug]
[--gradio-auth GRADIO_AUTH] [--gradio-img2img-tool {color-sketch,editor}] [--opt-channelslast]
[--styles-file STYLES_FILE] [--autolaunch] [--use-textbox-seed] [--disable-console-progressbars]
[--enable-console-prompts] [--disable-safe-unpickle]
launch.py: error: unrecognized arguments: --api
Press any key to continue . . .