docs: def compute_arxiv_re(report_pattern, report_number):
      """Compute arXiv report-number."""
      if report_number is None:
          report_number = r"\g<name>"
      report_re = re.compile(r"(?<!<cds\.REPORTNUMBER>)(?<!\w)" +
                             "(?P<name>" + report_pattern + ")" +
                             old_arxiv_numbers, re.U | re.I)
      return report_re, report_number