def temperature_series(self, unit='kelvin'):
        """Returns the temperature time series relative to the meteostation, in
        the form of a list of tuples, each one containing the couple
        timestamp-value

        :param unit: the unit of measure for the temperature values. May be
            among: '*kelvin*' (default), '*celsius*' or '*fahrenheit*'
        :type unit: str
        :returns: a list of tuples
        :raises: ValueError when invalid values are provided for the unit of
            measure
        """
        if unit not in ('kelvin', 'celsius', 'fahrenheit'):
            raise ValueError("Invalid value for parameter 'unit'")
        result = []
        for tstamp in self._station_history.get_measurements():
            t = self._station_history.get_measurements()[tstamp]['temperature']
            if unit == 'kelvin':
                temp = t
            if unit == 'celsius':
                temp = temputils.kelvin_to_celsius(t)
            if unit == 'fahrenheit':
                temp = temputils.kelvin_to_fahrenheit(t)
            result.append((tstamp, temp))
        return result
Returns the temperature time series relative to the meteostation, in
        the form of a list of tuples, each one containing the couple
        timestamp-value

        :param unit: the unit of measure for the temperature values. May be
            among: '*kelvin*' (default), '*celsius*' or '*fahrenheit*'
        :type unit: str
        :returns: a list of tuples
        :raises: ValueError when invalid values are provided for the unit of
            measure