XML convert property to an attribute not working

[dcrawford1]

Adding xml/attribute: true to a property should convert it to a XML attribute. The example from swagger

book:
  type: object
  properties:
    id:
      type: integer
      xml:
        attribute: true
    title:
      type: string
    author:
      type: string

should render as:

<book id="0">
  <title>string</title>
  <author>string</author>
</book>

But in Rapidoc id is still a regular XML property:

<?xml version="1.0" encoding="UTF-8"?>
<root>
  <id>0</id>
  <title>string</title>
  <author>string</author>
</root>