Function work_to_do

fn work_to_do<'a, BaseJob, MergeJob, I>(
    trees: I,
    max_base_jobs: u64,
) -> Vec<AvailableJob<BaseJob, MergeJob>>
where
    I: Iterator<Item = &'a Tree<Base<BaseJob>, Merge<MergeJob>>>,
    BaseJob: Debug + Clone + 'static,
    MergeJob: Debug + Clone + 'static,