Function parse_generic_spread_id_legs 

pub fn parse_generic_spread_id_legs(
    instrument_id: &InstrumentId,
) -> Result<Vec<(InstrumentId, i64)>>

Parses a generic spread instrument ID into (instrument_id, ratio) legs.

Accepts the format new_generic_spread_id produces and returns the legs in the order they appear in the symbol, with a negative ratio for each ((ratio))symbol leg. Each ratio must be non-zero and contain only ASCII digits, so a sign inside the parentheses is rejected.

Errors

Returns an error if:

• The symbol does not contain GENERIC_SPREAD_ID_SEPARATOR.
• A leg is not in the (ratio)symbol or ((ratio))symbol format.