code: def is_tRNA(clus_obj, out_dir, args):
      
      ref = os.path.abspath(args.reference)
      utils.safe_dirs(out_dir)
      for nc in clus_obj[0]:
          c = clus_obj[0][nc]
          loci = c['loci']
          out_fa = "cluster_" + nc
          if loci[0][3] - loci[0][2] < 500:
              with make_temp_directory() as tmpdir:
                  os.chdir(tmpdir)
                  get_loci_fasta({loci[0][0]: [loci[0][0:5]]}, out_fa, ref)
                  summary_file, str_file = _run_tRNA_scan(out_fa)
                  if "predictions" not in c:
                      c['predictions'] = {}
                  c['predictions']['tRNA'] = _read_tRNA_scan(summary_file)
                  score = _read_tRNA_scan(summary_file)
                  logger.debug(score)
                  shutil.move(summary_file, op.join(out_dir, summary_file))
                  shutil.move(str_file, op.join(out_dir, str_file))
          else:
              c['errors'].add("precursor too long")
          clus_obj[0][nc] = c
  
      return clus_obj
docs: Iterates through cluster precursors to predict sRNA types