Update app.py

app.py

@@ -110,7 +110,7 @@ def process_user_question(user_question):
 
     print('process_user_question called: \n')
 
-    if (! SESSION_STARTED):
+    if not SESSION_STARTED:
         print('No Session')
         st.write( 'Please upload and analyze your PDF files first!')
         return