Update app.py

app.py

@@ -21,10 +21,10 @@ def get_api_key():
     return api_key
 
 def set_model(model):
-    os.environ["model_type"] = model
+    os.environ["OPENAI_MODEL"] = model
 
 def get_model():
-    model = os.getenv("model_type")
+    model = os.getenv("OPENAI_MODEL")
     return model    
 
 def respond(message, chat_history):