Function black_scholes_with_moments 

pub fn black_scholes_with_moments(
    option_type: &OptionType,
    spot: f64,
    strike: f64,
    time_to_expiry: f64,
    risk_free_rate: f64,
    volatility: f64,
    skew: f64,
    excess_kurtosis: f64,
) -> f64