Function extract_market_id 

pub fn extract_market_id(instrument_id: &InstrumentId) -> Result<String>

Extracts the Betfair market ID from a Nautilus instrument ID.

Instrument IDs follow the format {market_id}-{selection_id}.BETFAIR or {market_id}-{selection_id}-{handicap}.BETFAIR.

Errors

Returns an error if the symbol does not contain a hyphen separator.