code: def filter_junction_variants(vrn_file, data):
      
      SJ_BP_MASK = 10
      vrn_dir = os.path.dirname(vrn_file)
      splicebed = dd.get_junction_bed(data)
      if not file_exists(splicebed):
          logger.info("Splice junction BED file not found, skipping filtering of "
                      "variants closed to splice junctions.")
          return vrn_file
      spliceslop = get_padded_bed_file(vrn_dir, splicebed, SJ_BP_MASK, data)
      out_file = os.path.splitext(vrn_file)[0] + "-junctionfiltered.vcf.gz"
      if file_exists(out_file):
          return out_file
      with file_transaction(data, out_file) as tx_out_file:
          out_base = os.path.splitext(tx_out_file)[0]
          logger.info("Removing variants within %d bases of splice junctions listed in %s from %s. " % (SJ_BP_MASK, spliceslop, vrn_file))
          pybedtools.BedTool(vrn_file).intersect(spliceslop, wa=True, header=True, v=True).saveas(out_base)
          tx_out_file = vcfutils.bgzip_and_index(out_base, dd.get_config(data))
      return out_file
docs: filter out variants within 10 basepairs of a splice junction, these are
      very prone to being false positives with RNA-seq data