fix defaults

app.py

@@ -180,7 +180,7 @@ if __name__ == "__main__":
         css=".underline-on-hover:hover { text-decoration: underline; } .flagging { font-size:12px; color:Silver; }"
     )
 
-    def submit(query, lang, k):
+    def submit(query, lang="en", k=10):
         if query == "":
             raise ValueError("Invalid query provided")
         return {