Function try_par_for_each_in 

pub fn try_par_for_each_in<T: Dss, E: DynSend>(
    items: &(impl ParSlice<T> + ?Sized),
    for_each: impl Fn(&T) -> Result<(), E> + Dss,
) -> Result<(), E>

This runs for_each in parallel for each iterator item. If one or more of the for_each calls returns Err, the function will also return Err. The error returned will be non-deterministic, but this is expected to be used with ErrorGuaranteed which are all equivalent.