def _build_command(self, cmds, sync=False):
        """Build full EOS's openstack CLI command.

        Helper method to add commands to enter and exit from openstack
        CLI modes.

        :param cmds: The openstack CLI commands that need to be executed
                     in the openstack config mode.
        :param sync: This flags indicates that the region is being synced.
        """

        region_cmd = 'region %s' % self.region
        if sync:
            region_cmd = self.cli_commands[const.CMD_REGION_SYNC]

        full_command = [
            'enable',
            'configure',
            'cvx',
            'service openstack',
            region_cmd,
        ]
        full_command.extend(cmds)
        return full_command