Function plan_insert_order 

pub fn plan_insert_order<T, S>(
    mappers: &HashMap<String, TableMapper>,
    paths: &[S],
    joins: &mut Vec<HashSet<String>>,
    merges: &mut HashSet<String>,
    partials: &mut Vec<HashSet<String>>,
) -> Result<(), ToqlError>
where
    S: AsRef<str>,
    T: Mapped,