def add_series(series)
      raise ArgumentError, "Invalid argument 'series' Expected ImageSeries or DoseVolume, got #{series.class}." unless [ImageSeries, DoseVolume].include?(series.class)
      @image_series << series
      @associated_series[series.uid] = series
    end
def add_series(series)
      raise ArgumentError, "Invalid argument 'series' Expected ImageSeries or DoseVolume, got #{series.class}." unless [ImageSeries, DoseVolume].include?(series.class)
      @image_series << series
      @associated_series[series.uid] = series
    end
Adds an ImageSeries to this Frame.

 @param [ImageSeries, DoseVolume] series an image series instance to be associated with this frame