def method_missing(name,*args,&block)
      self.class.send :define_method,"parse_#{name}" do |node,contents|
        block.call node,contents
      end
    end
def method_missing(name,*args,&block)
      self.class.send :define_method,"parse_#{name}" do |node,contents|
        block.call node,contents
      end
    end
define custom node processor