code: def add_report_number(self, report_number, source=None):
          
          self._append_to('report_numbers', self._sourced_dict(
              source,
              value=report_number,
          ))
docs: Add report numbers.
  
          :param report_number: report number for the current document
          :type report_number: string
  
          :param source: source for the given report number
          :type source: string