final Block block = (Block) node;
/* ... which contains an InstreamForeignObject ... */
node = block.getChildAt(0);
assertTrue(node instanceof InstreamForeignObject);
final InstreamForeignObject ifo = (InstreamForeignObject) node;
/* ... which contains an SVGElement ... */
node = ifo.getChildAt(0);
assertTrue(node instanceof InstreamSvgElement);
final InstreamSvgElement svgElement = (InstreamSvgElement) node;
/* ... for which we can find the width and height. */