Function new_generic_spread_id 

pub fn new_generic_spread_id(
    instrument_ratios: &[(InstrumentId, i64)],
) -> Result<InstrumentId>

Creates a generic spread instrument ID from (instrument_id, ratio) legs.

Sorts the legs by symbol and joins them with GENERIC_SPREAD_ID_SEPARATOR, formatting a positive ratio as (ratio)symbol and a negative ratio as ((ratio))symbol. For example, MSFT.NASDAQ with ratio 1 and AAPL.NASDAQ with ratio -2 produce ((2))AAPL___(1)MSFT.NASDAQ.

A leg symbol that contains the separator or ends with _ produces an ID that does not parse back into the same legs.

Errors

Returns an error if:

• Fewer than two legs are given.
• A ratio is zero or i64::MIN.
• The legs have different venues.