How to use the vega-scenegraph.boundStroke function in vega-scenegraph

y = offset + height;
      s = Math.max(minExtent, Math.min(maxExtent, bounds.y2));
      if (title) {
        title.y = titlePadding + s;
        s += titleSize;
      }
      bounds.add(0, y).add(width, y + s);
      break;
    }
  }

  item.x = x + 0.5;
  item.y = y + 0.5;

  // update bounds
  boundStroke(bounds, item);
  item.mark.bounds.clear().union(bounds);
  return bounds;
}

y += height - h - offset;
      break;
    case 'bottom-right':
      x += width - w - offset;
      y += height - h - offset;
      break;
  }

  // update legend layout
  item.x = x;
  item.y = y;
  item.width = w;
  item.height = h;

  // update bounds
  boundStroke(bounds.set(x, y, x + w, y + h), item);
  item.mark.bounds.clear().union(bounds);
  return bounds;
}

if (title) if (title.auto) {
        s += titlePadding;
        title.y = s;
        s += title.bounds.height();
      } else {
        bounds.union(title.bounds);
      }
      bounds.add(0, 0).add(range, s);
      break;
    default:
      x = item.x;
      y = item.y;
  }

  // update bounds
  boundStroke(bounds.translate(x, y), item);

  if (set(item, 'x', x + AxisOffset) | set(item, 'y', y + AxisOffset)) {
    item.bounds = tempBounds;
    view.dirty(item);
    item.bounds = bounds;
    view.dirty(item);
  }

  return item.mark.bounds.clear().union(bounds);
}

break;
    case 'bottom-left':
      x += offset;
      y += height - h - offset;
      break;
    case 'bottom-right':
      x += width - w - offset;
      y += height - h - offset;
      break;
    default:
      x = item.x;
      y = item.y;
  }

  // update bounds
  boundStroke(bounds.set(x, y, x + w, y + h), item);

  // update legend layout
  if (set(item, 'x', x) | set(item, 'width', w) |
      set(item, 'y', y) | set(item, 'height', h)) {
    item.bounds = tempBounds;
    view.dirty(item);
    item.bounds = bounds;
    view.dirty(item);
  }

  return item.mark.bounds.clear().union(bounds);
}

break;
    case 'bottom-left':
      x += offset;
      y += height - h - offset;
      break;
    case 'bottom-right':
      x += width - w - offset;
      y += height - h - offset;
      break;
    default:
      x = item.x;
      y = item.y;
  }

  // update bounds
  boundStroke(bounds.set(x, y, x + w, y + h), item);

  // update legend layout
  if (set(item, 'x', x) | set(item, 'width', w) |
      set(item, 'y', y) | set(item, 'height', h)) {
    item.bounds = tempBounds;
    view.dirty(item);
    item.bounds = bounds;
    view.dirty(item);
  }

  return item.mark.bounds.clear().union(bounds);
}

if (!bounds.empty()) {
    w = Math.ceil(bounds.width() + w);
    h = Math.ceil(bounds.height() + h);
  }

  if (datum.type === Symbols) {
    legendEntryLayout(item.items[0].items[0].items[0].items);
  }

  if (orient !== None) {
    item.x = x = 0;
    item.y = y = 0;
  }
  item.width = w;
  item.height = h;
  boundStroke(bounds.set(x, y, x + w, y + h), item);
  item.mark.bounds.clear().union(bounds);

  return item;
}