public int getSubIntervalCount(Comparable rowKey, Comparable columnKey) {
        int result = 0;
        int row = getRowIndex(rowKey);
        TaskSeries series = (TaskSeries) this.data.get(row);
        Task task = series.get(columnKey.toString());
        if (task != null) {
            result = task.getSubtaskCount();
        }
        return result;