How to set the parameter of the biobert

[201720502wrl]

I copy the following into the code,but report an error:
export
SAVE_DIR=./output
export
DATA_DIR=../datasets/NER
export
MAX_LENGTH=128
export
BATCH_SIZE=32
export
NUM_EPOCHS=30
export
SAVE_STEPS=1000
export
ENTITY=NCBI-disease
export
SEED=1
python
run_ner.py

--data_dir
${DATA_DIR}/${ENTITY}/

--labels
${DATA_DIR}/${ENTITY}/labels.txt

--model_name_or_path
dmis-lab/biobert-base-cased-v1.1

--output_dir
${SAVE_DIR}/${ENTITY}

--max_seq_length
${MAX_LENGTH}

--num_train_epochs
${NUM_EPOCHS}

--per_device_train_batch_size
${BATCH_SIZE}

--save_steps
${SAVE_STEPS}

--seed
${SEED}

--do_train

--do_eval

--do_predict

--overwrite_output_dir

run_ner.py: error: argument --max_seq_length: invalid int value: '${MAX_LENGTH}'
How to modify?Help!