     fileprivate let indentPrefixSymbol = " "
     
     
-    fileprivate func indentTextWithOffset(text: String, offset: Int) -> String {
+    fileprivate func indentTextWithOffset(_ text: String, _ offset: Int) -> String {
         if self.indent != 0 {
             let prefix = String(repeating: indentPrefixSymbol, count:self.indent)
             return "\n\(String(repeating: prefix, count:offset))\(text)"

    
    fileprivate func serialize(node: Node, offset: Int) -> String {
        if let shape = node as? Shape {
            return indentTextWithOffset(text: macawShapeToSvgShape(macawShape: shape), offset: offset)
        }
        if let group = node as? Group {
            var result = indentTextWithOffset(text: SVGGroupOpenTag, offset: offset)
            for child in group.contentsVar.value {
                result += serialize(node: child, offset: offset + 1)
            }
            result += indentTextWithOffset(text: SVGGroupCloseTag, offset: offset)
            return result
        }
        return SVGUndefinedTag

    fileprivate func serialize(node:Node) -> String {
        var result = [SVGDefaultHeader, "id=\"\(self.id)\"", "width=\"\(self.width)\"", "height=\"\(self.height)\"", SVGGenericEndTag].joined(separator: " ")
        result += serialize(node: node, offset: 1)
        result += indentTextWithOffset(SVGFooter, 0)
        return result
    }
    
