'Prints Prefixlen/Netmask.
Not really. In fact it is our universal Netmask/Prefixlen printer.
This is considered an internal function.
want == 0 / None        don\'t return anything    1.2.3.0
want == 1               /prefix                  1.2.3.0/24
want == 2               /netmask                 1.2.3.0/255.255.255.0
want == 3               -lastip                  1.2.3.0-1.2.3.255'

def _printPrefix(self, want):

    if (((self._ipversion == 4) and (self._prefixlen == 32)) or ((self._ipversion == 6) and (self._prefixlen == 128))):
        if self.NoPrefixForSingleIp:
            want = 0
    if (want == None):
        want = self.WantPrefixLen
        if (want == None):
            want = 1
    if want:
        if (want == 2):
            netmask = self.netmask()
            if (not isinstance(netmask, INT_TYPES)):
                netmask = netmask.int()
            return ('/%s' % intToIp(netmask, self._ipversion))
        elif (want == 3):
            return ('-%s' % intToIp(((self.ip + self.len()) - 1), self._ipversion))
        else:
            return ('/%d' % self._prefixlen)
    else:
        return ''
