def systemEventSSE(symbols=None, on_data=None, token='<STR_LIT>', version='<STR_LIT>'):
return _runSSE('<STR_LIT>', symbols, on_data, token, version)<EOL>
The System event message is used to indicate events that apply to the market or the data feed.

    There will be a single message disseminated per channel for each System Event type within a given trading session.

    https://iexcloud.io/docs/api/#deep-system-event

    Args:
        symbols (string); Tickers to request
        on_data (function): Callback on data
        token (string); Access token
        version (string); API version