Update app.py

app.py

@@ -19,7 +19,7 @@ import os
 hf_token = os.getenv('HF_TOKEN')
 
 API_URL = "https://api-inference.huggingface.co/models/stabilityai/stable-diffusion-xl-base-1.0"
-headers = {"Authorization": "Bearer {hf_token}"}
+headers = {"Authorization": f"Bearer {hf_token}"}
 
 def query(payload):
     response = requests.post(API_URL, headers=headers, json=payload)