如何在Scala中生成格式良好的XML？

import scala.xml._

val person =
 <person>
    <name>John Doe</name>
    <age>30</age>
    <city>New York</city>
  </person>

val xmlString = person.toString()

println(xmlString)

  <name>John Doe</name>
  <age>30</age>
  <city>New York</city>
</person>

val personWithAttributes =
 <person id="1">
    <name>John Doe</name>
    <age>30</age>
    <city>New York</city>
  </person>