Function resolve_sunspec 

pub async fn resolve_sunspec<T: Transport>(
    t: &mut T,
    space: AddressSpace,
    anchors: &[u16],
    model_id: u16,
) -> Result<u16, Error<T::Error>>

Probe SunSpec anchors, walk the (model_id, length) chain, and return the offset of the target model’s ID register (spec §7.3; generated discovery blocks cache the result).