added session_subscribe() to __on()

Author: shbenzer

py/selenium/webdriver/common/bidi/network.py

@@ -108,6 +108,7 @@ def __continue_with_auth(self, request_id, username, password):
 
     def __on(self, event, callback):
         """Set a callback function to subscribe to a network event."""
+        self.conn.execute(session_subscribe(event))
         event = self.EVENTS.get(event, event)
         self.callbacks[event] = callback
         if len(self.subscriptions[event]) == 0: