def select(css_selector = nil, &block)
      if css_selector
        CssSelection.new(self, css_selector).each(&block)
      else
        Selection.new(self, block)
      end
    end
def select(css_selector = nil, &block)
      if css_selector
        CssSelection.new(self, css_selector).each(&block)
      else
        Selection.new(self, block)
      end
    end
Select nodes based on a css selector

 @param [String] css_selector
 @yieldparam [Hexp::Node]

 @return [Hexp::Selector,Hexp::CssSelector]

 @api public