code: def extract_submittable_jobs(waiting):
      
      submittable = set()            # Holds jobs that are able to be submitted
      # Loop over each job, and check all the subjobs in that job's dependency
      # list.  If there are any, and all of these have been submitted, then
      # append the job to the list of submittable jobs.
      for job in waiting:
          unsatisfied = sum([(subjob.submitted is False) for subjob in
                             job.dependencies])
          if unsatisfied == 0:
              submittable.add(job)
      return list(submittable)
docs: Obtain a list of jobs that are able to be submitted from the passed
      list of pending jobs
  
      - waiting           List of Job objects