'Add a single RR to the update section.'

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)
