It looks like the config file at './checkpoints/progen2-large' is not a valid JSON file.

[Eric Dou]

Cause:
Incorrect directory context of the pretrained models, i.e. progen2-large.

Solution:
mkdir progen2-large in ./checkpoints dir
mv config.json pytorch_model.bin ./progen2-large

rerun the python sample.py ****

Here's a solution for anyone who might run into this problem.