Returns global VPNv6 table.

        Creates the table if it does not exist.

def get_vpn6_table(self):
        """Returns global VPNv6 table.

        Creates the table if it does not exist.
        """
        vpn_table = self._global_tables.get(RF_IPv6_VPN)
        # Lazy initialize the table.
        if not vpn_table:
            vpn_table = Vpnv6Table(self._core_service, self._signal_bus)
            self._global_tables[RF_IPv6_VPN] = vpn_table
            self._tables[(None, RF_IPv6_VPN)] = vpn_table

        return vpn_table