Function route_double_hashmap_path 

pub fn route_double_hashmap_path<'a>(
    name: &'a str,
    my_prefix: &str,
    field_name: &str,
    inner_prefix: &str,
) -> Option<(&'a str, &'a str, String)>

For a #[nested] HashMap<String, HashMap<String, T>> field, parse a path <my_prefix>.<field_name>.<outer_key>.<inner_key>.<inner_suffix> and return (outer_key, inner_key, fully-qualified inner name for T::get_prop).

Returns None when the path doesn’t match (wrong prefix or too few segments).