heartbeat setting to AiohttpTransport does not prevent the idle connections from being closed

Setting heartbeat like this:

Client('ws://localhost:45940/gremlin', 'g', 
    transport_factory=lambda: transport.AiohttpTransport(heartbeat=5.0))

should send a ping message to the server to keep the connection alive but it clearly does not. Manual testing shows Gremlin Server closing the connection as idle despite this setting.

For more information on the setting see: https://docs.aiohttp.org/en/stable/client_reference.html