How to get the icon's svg string via plugin API?

Hi! everyone~ I want to get the icon’s svg string via plugin API, but I cant get implementation method from API Reference 。The svg string looks like this:

'<svg width="19" height="8" viewBox="0 0 19 8" fill="none" xmlns=""><rect x="0.333313" y="0.333313" width="18" height="7.33333" rx="1.33333" fill="black"/></svg>'

I know that I can get the svg string by following method。
But I should get it via figma plugin API :thinking:

This work is very urgent, hope to get your help, thank you very much!! :sparkles: