code: def combine_validations(items, vkey="validate"):
      
      csvs = set([])
      pngs = set([])
      for v in [x.get(vkey) for x in items]:
          if v and v.get("grading_summary"):
              csvs.add(v.get("grading_summary"))
          if v and v.get("grading_plots"):
              pngs |= set(v.get("grading_plots"))
      if len(csvs) == 1:
          grading_summary = csvs.pop()
      else:
          grading_summary = os.path.join(utils.safe_makedir(os.path.join(dd.get_work_dir(items[0]), vkey)),
                                         "grading-summary-combined.csv")
          with open(grading_summary, "w") as out_handle:
              for i, csv in enumerate(sorted(list(csvs))):
                  with open(csv) as in_handle:
                      h = in_handle.readline()
                      if i == 0:
                          out_handle.write(h)
                      for l in in_handle:
                          out_handle.write(l)
      return {"grading_plots": sorted(list(pngs)), "grading_summary": grading_summary}
docs: Combine multiple batch validations into validation outputs.