hpricot：Hpricot::Container::Trav#next_sibling

everyday Ruby 
>> require "hpricot"
=> true
>> doc = Hpricot('<p>foo1</p><p>foo2</p>')
=> #<Hpricot::Doc {elem <p> "foo1" </p>} {elem <p> "foo2" </p>}>
>> doc.at('p').next_sibling
=> {elem <p> "foo2" </p>}
>> doc.search('p')[1].next_sibling
=> nil
>> doc = Hpricot('<p>foo1</p><p>foo2</p><p>foo3</p>')
=> #<Hpricot::Doc {elem <p> "foo1" </p>} {elem <p> "foo2" </p>} {elem <p> "foo3" </p>}>
>> doc.at('p').next_sibling
=> {elem <p> "foo2" </p>}
>> doc.search('p')[1].next_sibling
=> {elem <p> "foo3" </p>}