Once training is completed, use the [~transformers.Trainer.evaluate] method to evaluate your model and get its perplexity:

import math
eval_results = trainer.evaluate()
print(f"Perplexity: {math.exp(eval_results['eval_loss']):.2f}")
Perplexity: 8.76

Then share your model to the Hub with the [~transformers.Trainer.push_to_hub] method so everyone can use your model:

trainer.push_to_hub()

If you aren't familiar with finetuning a model with Keras, take a look at the basic tutorial here!