def parse(node)
      node.xpath('*').each do |node_child|
        case node_child.name
        when 'spTree'
          @shape_tree = ShapeTree.new(parent: self).parse(node_child)
        when 'bg'
          @background = Background.new(parent: self).parse(node_child)
        end
      end
      self
    end
def parse(node)
      node.xpath('*').each do |node_child|
        case node_child.name
        when 'spTree'
          @shape_tree = ShapeTree.new(parent: self).parse(node_child)
        when 'bg'
          @background = Background.new(parent: self).parse(node_child)
        end
      end
      self
    end
Parse CommonSlideData object
 @param node [Nokogiri::XML:Element] node to parse
 @return [CommonSlideData] result of parsing