open System
open System.Xml
open System.IO
// your code goes here
let doc = XmlDocument()
doc.LoadXml("<?xml version='1.0'?>\n<root><test><child1/><child2/>foo<child3><child4/></child3></test></root>")
let writer = StringWriter()
doc.Save(writer)
printfn "%A" writer
b3BlbiBTeXN0ZW0Kb3BlbiBTeXN0ZW0uWG1sCm9wZW4gU3lzdGVtLklPCgovLyB5b3VyIGNvZGUgZ29lcyBoZXJlCmxldCBkb2MgPSBYbWxEb2N1bWVudCgpCmRvYy5Mb2FkWG1sKCI8P3htbCB2ZXJzaW9uPScxLjAnPz5cbjxyb290Pjx0ZXN0PjxjaGlsZDEvPjxjaGlsZDIvPmZvbzxjaGlsZDM+PGNoaWxkNC8+PC9jaGlsZDM+PC90ZXN0Pjwvcm9vdD4iKQoKbGV0IHdyaXRlciA9IFN0cmluZ1dyaXRlcigpCmRvYy5TYXZlKHdyaXRlcikKCnByaW50Zm4gIiVBIiB3cml0ZXI=