code: def _add_rr(self, name, ttl, rd, deleting=None, section=None):
          
  
          if section is None:
              section = self.authority
          covers = rd.covers()
          rrset = self.find_rrset(section, name, self.zone_rdclass, rd.rdtype,
                                  covers, deleting, True, True)
          rrset.add(rd, ttl)
docs: Add a single RR to the update section.