code: def _clean_regions(items, region):
      
      variant_regions = bedutils.population_variant_regions(items, merged=True)
      with utils.tmpfile() as tx_out_file:
          target = subset_variant_regions(variant_regions, region, tx_out_file, items)
          if target:
              if isinstance(target, six.string_types) and os.path.isfile(target):
                  target = _load_regions(target)
              else:
                  target = [target]
              return target
docs: Intersect region with target file if it exists