hpricot：Hpricot.build

everyday Ruby 
>> require "hpricot"
=> true
>> Hpricot.build
ArgumentError: block not supplied
  ...
>> Hpricot.build {}
=> #<Hpricot::Doc>
>> Hpricot.build(Hpricot('')) {}
=> #<Hpricot::Doc>
>> Hpricot.build(Hpricot(''), 'p' => '') {}
=> #<Hpricot::Doc>
>> Hpricot.build(Hpricot(''), 'p' => 'foo') {}
=> #<Hpricot::Doc>
>> Hpricot.build(Hpricot('')) { "<p>foo</p>"}
=> #<Hpricot::Doc>
>> Hpricot('') { }
=> #<Hpricot::Doc>