def parse(node)
      node.xpath('*').each do |nary_child_node|
        case nary_child_node.name
        when 'sub'
          @bottom_value = DocxFormula.new(parent: self).parse(nary_child_node)
        when 'sup'
          @top_value = DocxFormula.new(parent: self).parse(nary_child_node)
        when 'naryPr'
          @properties = NaryProperties.new(parent: self).parse(nary_child_node)
        end
      end
      self
    end
def parse(node)
      node.xpath('*').each do |nary_child_node|
        case nary_child_node.name
        when 'sub'
          @bottom_value = DocxFormula.new(parent: self).parse(nary_child_node)
        when 'sup'
          @top_value = DocxFormula.new(parent: self).parse(nary_child_node)
        when 'naryPr'
          @properties = NaryProperties.new(parent: self).parse(nary_child_node)
        end
      end
      self
    end
Parse Nary
 @param [Nokogiri::XML:Node] node with Nary
 @return [Nary] result of parsing