+ '''
+ api: Must be a newly created from arvados.api(cache=False), not shared with the caller, as it may be used by a background thread.
+ filters: Initial subscription filters.
+ on_event: The callback when a message is received
+ poll_fallback: If websockets are not available, fall back to polling every N seconds. If poll_fallback=False, this will return None if websockets are not available.
+ '''