code: @SuppressWarnings({"WeakerAccess", "unused"})
     public void  setDocumentHeight(String value) throws SVGParseException
     {
        if (this.rootElement == null)
           throw new IllegalArgumentException("SVG document is empty");
  
        this.rootElement.height = SVGParser.parseLength(value);
     }
docs: Change the height of the document by altering the "height" attribute
  of the root {@code <svg>} element.
  
  @param value A valid SVG 'length' attribute, such as "100px" or "10cm".
  @throws SVGParseException if {@code value} cannot be parsed successfully.
  @throws IllegalArgumentException if there is no current SVG document loaded.