Python-binance Websocket - ThreadedDepthCacheManager Error " 'NoneType' object has no attribute 'tld'

Hey guys,

I am trying to get the ThreadedDepthCacheManager from python-binance lib running.
This is the code:

 from binance import ThreadedDepthCacheManager

 dcm = ThreadedDepthCacheManager()

 def handle_depth_cache(depth_cache):
          print(f"symbol {depth_cache.symbol}")
          print("top 5 bids")
          print("last update time {}".format(depth_cache.update_time))

dcm_name = dcm.start_depth_cache(handle_depth_cache, symbol=symbol)


I just want to get the last top bid prices for BNB/BTC currency pair.
This is the error message:
'NoneType' object has no attribute 'tld' ----> dcm_name = dcm.start_depth_cache(handle_depth_cache, symbol=symbol)

Thank you in advance for your help!

BR Vegas913

Please look into the source code, which variable is NoneType