'Constructor.
Args:
friendly_name (string|func): Friendly name of sensor
field (string): Field name in the "current_observation"
dictionary.
icon (string): icon name or URL, if None sensor
will use current weather symbol
unit_of_measurement (string): unit of meassurement'

def __init__(self, friendly_name, field, icon='mdi:gauge', unit_of_measurement=None):

    super().__init__(friendly_name, 'conditions', value=(lambda wu: wu.data['current_observation'][field]), icon=icon, unit_of_measurement=unit_of_measurement, entity_picture=(lambda wu: (wu.data['current_observation']['icon_url'] if (icon is None) else None)), device_state_attributes={'date': (lambda wu: wu.data['current_observation']['observation_time'])})
