def tunable(self, obj):
        """A tunable resource maps against a backend..."""
        self.tune = dict()
        if 'tune' in obj:
            for tunable in MOUNT_TUNABLES:
                tunable_key = tunable[0]
                map_val(self.tune, obj['tune'], tunable_key)
                if tunable_key in self.tune and \
                   is_vault_time(self.tune[tunable_key]):
                    vault_time_s = vault_time_to_s(self.tune[tunable_key])
                    self.tune[tunable_key] = vault_time_s

        if 'description'in obj:
            self.tune['description'] = obj['description']
A tunable resource maps against a backend...