Plot.plot() attaches scale to whatever it returns. That is the <svg>
for a bare plot, but the <figure> when the plot has a title, subtitle,
caption, or legend — and in the wrapped case the inner <svg> carries
nothing. Callers hold either one depending on how they found the chart, so
this looks in both directions.
Finds the node carrying Plot's
scalefunction.Plot.plot()attachesscaleto whatever it returns. That is the<svg>for a bare plot, but the<figure>when the plot has a title, subtitle, caption, or legend — and in the wrapped case the inner<svg>carries nothing. Callers hold either one depending on how they found the chart, so this looks in both directions.