Function construct_custom_netdir_with_params_inner 

fn construct_custom_netdir_with_params_inner<F, P, PK>(
    func: F,
    params: P,
    lifetime: Option<Lifetime>,
    geoip_db: Option<&GeoipDb>,
) -> BuildResult<PartialNetDir>
where
    F: FnMut(usize, &mut NodeBuilders, &mut MdConsensusBuilder),
    P: IntoIterator<Item = (PK, i32)>,
    PK: Into<String>,

Implementation of construct_custom_netdir_with_params, written this way to avoid the GeoIP argument crossing a crate API boundary.