Error on loading training model "_pickle.UnpicklingError: invalid load key, '<'"

Hi, I have loaded all training models and running following code raise "_pickle.UnpicklingError: invalid load key, '<'" error.

`python inference.py -c config.json -f models/flowtron_ljs.pt -w models/waveglow_256channels_v4.pt -t "$tts_text" -i 0`