'Initialize the sensor.'

def __init__(self, name, state_topic, qos, unit_of_measurement, force_update, expire_after, value_template):

    self._state = STATE_UNKNOWN
    self._name = name
    self._state_topic = state_topic
    self._qos = qos
    self._unit_of_measurement = unit_of_measurement
    self._force_update = force_update
    self._template = value_template
    self._expire_after = expire_after
    self._expiration_trigger = None
