Returns global VPNv6 Flow Specification table.

        Creates the table if it does not exist.

def get_vpnv6fs_table(self):
        """Returns global VPNv6 Flow Specification table.

        Creates the table if it does not exist.
        """
        vpnv6fs_table = self._global_tables.get(RF_VPNv6_FLOWSPEC)
        # Lazy initialization of the table.
        if not vpnv6fs_table:
            vpnv6fs_table = VPNv6FlowSpecTable(self._core_service,
                                               self._signal_bus)
            self._global_tables[RF_VPNv6_FLOWSPEC] = vpnv6fs_table
            self._tables[(None, RF_VPNv6_FLOWSPEC)] = vpnv6fs_table

        return vpnv6fs_table