hpricot：Hpricot::Traverse#xmldecl?

everyday Ruby 
>> require "hpricot"
=> true
>> doc = Hpricot('<p><b>foo1</b>hoge</p><p>foo2</p>')
=> #<Hpricot::Doc {elem <p> {elem <b> "foo1" </b>} "hoge" </p>} {elem <p> "foo2" </p>}>
>> doc.xmldecl?
=> false
>> doc = Hpricot::XML("")
=> #<Hpricot::Doc>
>> doc.xmldecl?
=> false
>> doc = Hpricot::XML('<?xml version="1.0" encoding="UTF-8"?>')
=> #<Hpricot::Doc {xmldecl "<?xml version=\"1.0\" encoding=\"UTF-8\"?>"}>
>> doc.at('*')
=> {xmldecl "<?xml version=\"1.0\" encoding=\"UTF-8\"?>"}
>> doc.at('*').xmldecl?
=> true