/**
  * Removes the specified series from the collection.
  *
  * @param series the series to remove (<code>null</code> not permitted).
  */
 public void removeSeries(TimePeriodValues series) {
   ParamChecks.nullNotPermitted(series, "series");
   this.data.remove(series);
   series.removeChangeListener(this);
   fireDatasetChanged();
 }