如何通过BIRT图表API自定义系列填充区域图表？

I am trying to create a gradient fill for a series in an area chart that I am building through the BIRT chart API, but the book "Integrating and Extending BIRT" and the Interwebs seem curiously silent about how to get it to work. It seems no matter what I do, I always get a flat color from the default palette. I've tried using SeriesDefinition.getSeriesPalette().update(Gradient) and even creating my own Palette with the gradient fill in it and setting that on the SeriesDefinition, but to no avail. I've also noticed that if I do not perform a shift() on the Palette, even if it's shift(0), which the Javadocs claim will do nothing, I get NullPointerException when I try to generate the chart:I am trying to create a gradient fill for a ser