Construct a zone bound to this client.

        :type name: str
        :param name: Name of the zone.

        :type dns_name: str
        :param dns_name:
            (Optional) DNS name of the zone.  If not passed, then calls to
            :meth:`zone.create` will fail.

        :type description: str
        :param description:
            (Optional) the description for the zone.  If not passed, defaults
            to the value of 'dns_name'.

        :rtype: :class:`google.cloud.dns.zone.ManagedZone`
        :returns: a new ``ManagedZone`` instance.

def zone(self, name, dns_name=None, description=None):
        """Construct a zone bound to this client.

        :type name: str
        :param name: Name of the zone.

        :type dns_name: str
        :param dns_name:
            (Optional) DNS name of the zone.  If not passed, then calls to
            :meth:`zone.create` will fail.

        :type description: str
        :param description:
            (Optional) the description for the zone.  If not passed, defaults
            to the value of 'dns_name'.

        :rtype: :class:`google.cloud.dns.zone.ManagedZone`
        :returns: a new ``ManagedZone`` instance.
        """
        return ManagedZone(name, dns_name, client=self, description=description)