def ratio_value_number_to_time_series_length(self, x):
        """
            As in tsfresh `ratio_value_number_to_time_series_length <https://github.com/blue-yonder/tsfresh/blob/master\
            /tsfresh/feature_extraction/feature_calculators.py#L830>`_

            Returns a factor which is 1 if all values in the time series occur only once,
            and below one if this is not the case.
            In principle, it just returns: # unique values / # values
            
            :param x: the time series to calculate the feature of
            :type x: pandas.Series
            :return: the value of this feature
            :rtype: float
        """
        ratio = feature_calculators.ratio_value_number_to_time_series_length(x)
        logging.debug("ratio value number to time series length by tsfresh calculated")
        return ratio
As in tsfresh `ratio_value_number_to_time_series_length <https://github.com/blue-yonder/tsfresh/blob/master\
            /tsfresh/feature_extraction/feature_calculators.py#L830>`_

            Returns a factor which is 1 if all values in the time series occur only once,
            and below one if this is not the case.
            In principle, it just returns: # unique values / # values
            
            :param x: the time series to calculate the feature of
            :type x: pandas.Series
            :return: the value of this feature
            :rtype: float