Cayenne-MQTT-Python UNITS and Type

Hi
I am reading doc. of Cayenne-MQTT-Python.
I could not find Units of A and mA .

But I felt uneasy freeing about this document.
I could not understand about it.
Why I can not define Unit by myself (freely) ??

| virtualWrite(self, channel, value, dataType=’’, dataUnit=’’)

Does Cayenne need UNIT ?? or restriction ??
And
Data type is same.

Please let me know the reason!!

Thanks


UNIT_CELSIUS = 'c'
UNIT_CENTIMETER = 'cm'
UNIT_DIGITAL = 'd'
UNIT_FAHRENHEIT = 'f'
UNIT_HECTOPASCAL = 'hpa'
UNIT_KELVIN = 'k'
UNIT_LUX = 'lux'
UNIT_METER = 'm'
UNIT_MILLIVOLTS = 'mv'
UNIT_PASCAL = 'pa'
UNIT_PERCENT = 'p'
UNIT_RATIO = 'r'
UNIT_UNDEFINED = 'null'
UNIT_VOLTS = 'v'

TYPE_BAROMETRIC_PRESSURE = 'bp'
TYPE_BATTERY = 'batt'
TYPE_LUMINOSITY = 'lum'
TYPE_PROXIMITY = 'prox'
TYPE_RELATIVE_HUMIDITY = 'rel_hum'
TYPE_TEMPERATURE = 'temp'
TYPE_VOLTAGE = 'voltage'

it is necessary to use the correct unit type for the respective data types. you cannot define your own unit as we have limited data types which recognised by the server. have a look at all the data types here http://mydevices.com/cayenne/docs/cayenne-mqtt-api/#cayenne-mqtt-api-supported-data-types

Thank you
I must lean it !!