Returns a TimeSeriesRDD with missing values imputed using the given method.
        
        Parameters
        ----------
        method : string
            "nearest" fills in NaNs with the closest non-NaN value, using the closest previous value
            in the case of a tie.  "linear" does a linear interpolation from the closest filled-in
            values.  "next" uses the closest value that is in the future of the missing value.
            "previous" uses the closest value from the past of the missing value.  "spline"
            interpolates using a cubic spline.

def fill(self, method):
        """
        Returns a TimeSeriesRDD with missing values imputed using the given method.
        
        Parameters
        ----------
        method : string
            "nearest" fills in NaNs with the closest non-NaN value, using the closest previous value
            in the case of a tie.  "linear" does a linear interpolation from the closest filled-in
            values.  "next" uses the closest value that is in the future of the missing value.
            "previous" uses the closest value from the past of the missing value.  "spline"
            interpolates using a cubic spline.
        """
        return TimeSeriesRDD(None, None, self._jtsrdd.fill(method), self.ctx)