@staticmethod
def last_value(counter):
    """
        alphabetical sort data =)
        :param counter: counter JSON
        :return: float or None
        None - когда показания не сданы более 3-х месяцев
        """
    indications = counter['indications']
    indications.sort(key=lambda x: x['period'])
    if indications:
        return float(indications[-1]['indication'])
