code: def get_splicejunction_file(align_dir, data):
      
      samplename = dd.get_sample_name(data)
      align_dir = os.path.dirname(dd.get_work_bam(data))
      knownfile = get_known_splicesites_file(align_dir, data)
      novelfile = os.path.join(align_dir, "%s-novelsplicesites.bed" % samplename)
      bed_files = [x for x in [knownfile, novelfile] if file_exists(x)]
      splicejunction = bed.concat(bed_files)
      splicejunctionfile = os.path.join(align_dir,
                                        "%s-splicejunctions.bed" % samplename)
      if splicejunction:
          splicejunction.saveas(splicejunctionfile)
          return splicejunctionfile
      else:
          return None
docs: locate the splice junction file from hisat2. hisat2 outputs a novel
      splicesites file to go along with the provided file, if available.
      this combines the two together and outputs a combined file of all
      of the known and novel splice junctions