def update(message)
      unless message.nil?
        # Parse reading from message
        @latest_reading = Reading.from_xml(message)
        # Inform observers
        changed
        notify_observers(@latest_reading)
      end
    rescue CurrentCost::ParseError
      nil
    end
def update(message)
      unless message.nil?
        # Parse reading from message
        @latest_reading = Reading.from_xml(message)
        # Inform observers
        changed
        notify_observers(@latest_reading)
      end
    rescue CurrentCost::ParseError
      nil
    end
Internal use only, client code does not need to use this function. Informs
 the Meter object that a new message has been received by the serial port.