OSError: Can't load config for 'longformer-base-4096/'

1. I tried to run the code given on the github page but it gave me this error:
2. I have downloaded the pretrained model but I don't know which file should I put it, can anyone tell me?

Traceback (most recent call last):
File "/home/mist/.local/lib/python3.6/site-packages/transformers/configuration_utils.py", line 373, in get_config_dict
raise EnvironmentError
OSError

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "test.py", line 6, in
config = LongformerConfig.from_pretrained('longformer-base-4096/')
File "/home/mist/.local/lib/python3.6/site-packages/transformers/configuration_utils.py", line 329, in from_pretrained
config_dict, kwargs = cls.get_config_dict(pretrained_model_name_or_path, **kwargs)
File "/home/mist/.local/lib/python3.6/site-packages/transformers/configuration_utils.py", line 382, in get_config_dict
raise EnvironmentError(msg)
OSError: Can't load config for 'longformer-base-4096/'. Make sure that:

- 'longformer-base-4096/' is a correct model identifier listed on 'https://huggingface.co/models'

- or 'longformer-base-4096/' is the correct path to a directory containing a config.json file