Update app.py

app.py

@@ -1,6 +1,7 @@
 #ref: https://huggingface.co/blog/AmelieSchreiber/esmbind
 import gradio as gr
 
+import os
 from transformers import Trainer, TrainingArguments, AutoTokenizer, EsmForMaskedLM, TrainerCallback
 from torch.utils.data import DataLoader, Dataset, RandomSampler
 import pandas as pd