class ActionView::Helpers::AtomFeedHelper::AtomBuilder

if type: 'xhtml' is, in fact, specified.
in the Atom spec as potentially containing XHTML content and
True if the method name matches one of the five elements defined

def xhtml_block?(method, arguments)
  if XHTML_TAG_NAMES.include?(method.to_s)
    last = arguments.last
    last.is_a?(Hash) && last[:type].to_s == 'xhtml'
  end
end