src/vs/workbench/contrib/notebook/browser/notebookEditorDecorations.ts/NotebookDecorationCSSRules/_resolveValue
class NotebookDecorationCSSRules:	private _resolveValue(value: string | ThemeColor): string {
		if (isThemeColor(value)) {
			const color = this._theme.getColor(value.id);
			if (color) {
				return color.toString();
			}
			return 'transparent';
		}
		return value;
	}