code: def fill(self, method):
          
          return TimeSeriesRDD(None, None, self._jtsrdd.fill(method), self.ctx)
docs: 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.