[yt-users] Saving transparent pdfs

I'm having some trouble saving pdfs that are transparent using .save() with any of the PlotContainer inherited classes. Typically when I have access to the entire figure, plt.savefig has an optional argument Transparent=True that returns the desired result. I've tried to get the underlying figure with my SlicePlot for example, but I also have additional annotations (contours) and I'm not sure how to add these to the underlying figure in order to use plt.savefig. I see that the save function in PlotContainer creates a FigureCanvasPdf object which then calls print_figure (which calls print_pdf). This function does not have an argument for transparency. Thoughts?