'Enable or disable \'DNSSEC desired\' flag in requests.
@param wanted: Is DNSSEC desired?  If True, EDNS is enabled if
required, and then the DO bit is set.  If False, the DO bit is
cleared if EDNS is enabled.
@type wanted: bool'

def want_dnssec(self, wanted=True):

    if wanted:
        if (self.edns < 0):
            self.use_edns()
        self.ednsflags |= dns.flags.DO
    elif (self.edns >= 0):
        self.ednsflags &= (~ dns.flags.DO)
