code: def _add_region_params(region, out_file, items, gatk_type):
      
      params = []
      variant_regions = bedutils.population_variant_regions(items)
      region = subset_variant_regions(variant_regions, region, out_file, items)
      if region:
          if gatk_type == "gatk4":
              params += ["-L", bamprep.region_to_gatk(region), "--interval-set-rule", "INTERSECTION"]
          else:
              params += ["-L", bamprep.region_to_gatk(region), "--interval_set_rule", "INTERSECTION"]
      params += gatk.standard_cl_params(items)
      return params
docs: Add parameters for selecting by region to command line.