Generate an `aid` element with `libxml-ruby`

[Qualeto]

The spec for ICML requires two \[code\]<?aid?>\[/code\] elements in the prolog of a document. For example:\[code\]<?xml version="1.0" encoding="UTF-8" standalone="yes"?><?aid style="50" type="snippet" readerVersion="7.0" featureSet="257" product="7.0(232)" ?><?aid SnippetType="PageItem"?><Document DOMVersion="7.0" Self="d"> ...</Document>\[/code\]How can I generate these elements using \[code\]libxml-ruby\[/code\]? Are these processing instructions?