changing sources to f string

app.py

@@ -86,7 +86,7 @@ def respond(message, history):
             yield response
 
     usedSections = list(dict.fromkeys(topSections))
-    citation = "\n\n\* 📋 Sources: " + ", ".join(usedSections) + "*"
+    citation = f"\n\n *📋 Sources: {usedSections}*"
     yield response + citation
 
 custom_css = """