Websocket transport session does not exist or has already disconnected - Python

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1

Writing a websocket client and eventsub subscription request in python, websocket recieves welcome message and functions seemingly correctly, but returns error 400, seen above, upon sending the subscription request:

async def listen():
  url = "wss://eventsub.wss.twitch.tv/ws"

  async with websockets.connect(url) as websocket: 
    msg = await websocket.recv()
    msg_dic = json.loads(msg)
    seshId = (msg_dic["payload"]["session"]["id"])
    global sessionID 
    sessionID = seshId
  
asyncio.get_event_loop().run_until_complete(listen())

async def post_request():
  async with aiohttp.ClientSession() as session:
      response = await session.post(url="https://api.twitch.tv/helix/eventsub/subscriptions",
                                    data=json.dumps({"type":"stream.online",
                                         "version": "1",
                                         "condition":{
                                           "broadcaster_user_id": "------"},
                                         "transport":{
                                           "method":"websocket",
                                           "session_id":sessionID}}),                                                            
                                    headers={'Authorization': 'Bearer ---------',
                                             'Client-Id': '----------',
                                            "Content-Type": "application/json",})
      print(await response.json())
asyncio.run(post_request())