text: Title: Optimizer file [/home/weidawang/.paddle/weights/BMN.pdopt] not exits
  Body: I got error when i am getting started with BMN:
  
  ```
  (base) weidawang@weidawang-TUF-Gaming-FX506LU-FX506LU:~/Repo/PaddlePaddle/models/PaddleCV/video$ bash run.sh predict BMN ./configs/bmn.yaml
  predict BMN ./configs/bmn.yaml
  DALI is not installed, you can improve performance if use DALI
  [INFO: predict.py:  199]: Namespace(batch_size=1, config='./configs/bmn.yaml', filelist=None, infer_topk=20, log_interval=1, model_name='BMN', save_dir='data/predict_results', use_gpu=True, video_path='', weights=None)
  [INFO: config_utils.py:   70]: ---------------- Infer Arguments ----------------
  [INFO: config_utils.py:   72]: MODEL:
  [INFO: config_utils.py:   74]:     name:BMN
  [INFO: config_utils.py:   74]:     tscale:100
  [INFO: config_utils.py:   74]:     dscale:100
  [INFO: config_utils.py:   74]:     feat_dim:400
  [INFO: config_utils.py:   74]:     prop_boundary_ratio:0.5
  [INFO: config_utils.py:   74]:     num_sample:32
  [INFO: config_utils.py:   74]:     num_sample_perbin:3
  [INFO: config_utils.py:   74]:     anno_file:data/dataset/bmn/activitynet_1.3_annotations.json
  [INFO: config_utils.py:   74]:     feat_path:/media/weidawang/DATA/dataset/ActionLocalization/bmn_feat
  [INFO: config_utils.py:   72]: TRAIN:
  [INFO: config_utils.py:   74]:     subset:train
  [INFO: config_utils.py:   74]:     epoch:9
  [INFO: config_utils.py:   74]:     batch_size:16
  [INFO: config_utils.py:   74]:     num_threads:8
  [INFO: config_utils.py:   74]:     use_gpu:True
  [INFO: config_utils.py:   74]:     num_gpus:4
  [INFO: config_utils.py:   74]:     learning_rate:0.001
  [INFO: config_utils.py:   74]:     learning_rate_decay:0.1
  [INFO: config_utils.py:   74]:     lr_decay_iter:4200
  [INFO: config_utils.py:   74]:     l2_weight_decay:0.0001
  [INFO: config_utils.py:   72]: VALID:
  [INFO: config_utils.py:   74]:     subset:validation
  [INFO: config_utils.py:   74]:     batch_size:16
  [INFO: config_utils.py:   74]:     num_threads:8
  [INFO: config_utils.py:   74]:     use_gpu:True
  [INFO: config_utils.py:   74]:     num_gpus:4
  [INFO: config_utils.py:   72]: TEST:
  [INFO: config_utils.py:   74]:     subset:validation
  [INFO: config_utils.py:   74]:     batch_size:1
  [INFO: config_utils.py:   74]:     num_threads:1
  [INFO: config_utils.py:   74]:     snms_alpha:0.001
  [INFO: config_utils.py:   74]:     snms_t1:0.5
  [INFO: config_utils.py:   74]:     snms_t2:0.9
  [INFO: config_utils.py:   74]:     output_path:data/output/EVAL/BMN_results
  [INFO: config_utils.py:   74]:     result_path:data/evaluate_results
  [INFO: config_utils.py:   72]: INFER:
  [INFO: config_utils.py:   74]:     subset:test
  [INFO: config_utils.py:   74]:     batch_size:1
  [INFO: config_utils.py:   74]:     num_threads:1
  [INFO: config_utils.py:   74]:     snms_alpha:0.4
  [INFO: config_utils.py:   74]:     snms_t1:0.5
  [INFO: config_utils.py:   74]:     snms_t2:0.9
  [INFO: config_utils.py:   74]:     filelist:data/dataset/bmn/infer.list
  [INFO: config_utils.py:   74]:     output_path:data/output/INFER/BMN_results
  [INFO: config_utils.py:   74]:     result_path:data/predict_results
  [INFO: config_utils.py:   75]: -------------------------------------------------
  W1218 16:29:50.778240 31472 device_context.cc:338] Please NOTE: device: 0, CUDA Capability: 75, Driver API Version: 11.1, Runtime API Version: 10.2
  W1218 16:29:50.779249 31472 device_context.cc:346] device: 0, cuDNN Version: 8.0.
  test subset video numbers: 5
  Traceback (most recent call last):
    File "predict.py", line 201, in <module>
      infer(args)
    File "predict.py", line 132, in infer
      fluid.default_main_program(), place)
    File "/home/weidawang/Repo/PaddlePaddle/models/PaddleCV/video/models/model.py", line 158, in load_test_weights
      fluid.load(prog, weights, executor=exe, var_list=params_list)
    File "<decorator-gen-76>", line 2, in load
    File "/home/weidawang/miniconda3/lib/python3.7/site-packages/paddle/fluid/wrapped_decorator.py", line 25, in __impl__
      return wrapped_func(*args, **kwargs)
    File "/home/weidawang/miniconda3/lib/python3.7/site-packages/paddle/fluid/framework.py", line 215, in __impl__
      return func(*args, **kwargs)
    File "/home/weidawang/miniconda3/lib/python3.7/site-packages/paddle/fluid/io.py", line 1882, in load
      "Optimizer file [{}] not exits".format(opt_file_name)
  AssertionError: Optimizer file [/home/weidawang/.paddle/weights/BMN.pdopt] not exits
  ```
  