def parse(node)
      node.xpath('mc:Choice/*', 'xmlns:mc' => 'http://schemas.openxmlformats.org/markup-compatibility/2006').each do |node_child|
        case node_child.name
        when 'timing'
          @timing = Timing.new(parent: self).parse(node_child)
        when 'transition'
          @transition = Transition.new(parent: self).parse(node_child)
        when 'sp'
          @elements << DocxShape.new(parent: self).parse(node_child)
        end
      end
      self
    end
def parse(node)
      node.xpath('mc:Choice/*', 'xmlns:mc' => 'http://schemas.openxmlformats.org/markup-compatibility/2006').each do |node_child|
        case node_child.name
        when 'timing'
          @timing = Timing.new(parent: self).parse(node_child)
        when 'transition'
          @transition = Transition.new(parent: self).parse(node_child)
        when 'sp'
          @elements << DocxShape.new(parent: self).parse(node_child)
        end
      end
      self
    end
Parse PresentationAlternateContent object
 @param node [Nokogiri::XML:Element] node to parse
 @return [PresentationAlternateContent] result of parsing