class ActionView::Helpers::AtomFeedHelper::AtomBuilder

def method_missing(method, *arguments, &block)

that an xhtml_block? is desired.
namespaced div element if the method and arguments indicate
Delegate to XML Builder, first wrapping the element in an XHTML 
def method_missing(method, *arguments, &block)
  if xhtml_block?(method, arguments)
    @xml.__send__(method, *arguments) do
      @xml.div(xmlns: "http://www.w3.org/1999/xhtml") do |xhtml|
        block.call(xhtml)
      end
    end
  else
    @xml.__send__(method, *arguments, &block)
  end
end