code: @SuppressWarnings({"WeakerAccess", "unused"})
     public void  setDocumentHeight(float pixels)
     {
        if (this.rootElement == null)
           throw new IllegalArgumentException("SVG document is empty");
  
        this.rootElement.height = new Length(pixels);
     }
docs: Change the height of the document by altering the "height" attribute
  of the root {@code <svg>} element.
  
  @param pixels The new value of height in pixels.
  @throws IllegalArgumentException if there is no current SVG document loaded.