'Set the transition time for the brightness value.
Zwave Dimming Duration values:
0x00      = instant
0x01-0x7F = 1 second to 127 seconds
0x80-0xFE = 1 minute to 127 minutes
0xFF      = factory default'

def _set_duration(self, **kwargs):

    if (self.values.dimming_duration is None):
        if (ATTR_TRANSITION in kwargs):
            _LOGGER.debug('Dimming    not    supported    by    %s.', self.entity_id)
        return
    if (ATTR_TRANSITION not in kwargs):
        self.values.dimming_duration.data = 255
        return
    transition = kwargs[ATTR_TRANSITION]
    if (transition <= 127):
        self.values.dimming_duration.data = int(transition)
    elif (transition > 7620):
        self.values.dimming_duration.data = 254
        _LOGGER.warning('Transition    clipped    to    127    minutes    for    %s.', self.entity_id)
    else:
        minutes = int((transition / 60))
        _LOGGER.debug('Transition    rounded    to    %d    minutes    for    %s.', minutes, self.entity_id)
        self.values.dimming_duration.data = (minutes + 127)
