'Constructor.
Args:
friendly_name (string|func): Friendly name
feature (string): WU feature. See:
https://www.wunderground.com/weather/api/d/docs?d=data/index
value (function(WUndergroundData)): callback that
extracts desired value from WUndergroundData object
unit_of_measurement (string): unit of meassurement
entity_picture (string): value or callback returning
URL of entity picture
icon (string): icon name or URL
device_state_attributes (dict): dictionary of attributes,
or callable that returns it'

def __init__(self, friendly_name, feature, value, unit_of_measurement=None, entity_picture=None, icon='mdi:gauge', device_state_attributes=None):

    self.friendly_name = friendly_name
    self.unit_of_measurement = unit_of_measurement
    self.feature = feature
    self.value = value
    self.entity_picture = entity_picture
    self.icon = icon
    self.device_state_attributes = (device_state_attributes or {})
