Function metfor::dew_point_from_p_and_specific_humidity

pub fn dew_point_from_p_and_specific_humidity<P>(
    pressure: P, 
    q: f64
) -> Option<Celsius> where
    P: Pressure,
    HectoPascal: From<P>, 

Given a specific humidity and pressure, calculate the dew point temperature. If saturation is assumed, this is also the temperature.