def define(&block)
      if block && block.arity > 0
        block.call @ns
      elsif block
        @ns.instance_eval(&block)
      end
      @ns
    end
def define(&block)
      if block && block.arity > 0
        block.call @ns
      elsif block
        @ns.instance_eval(&block)
      end
      @ns
    end
define the parent ns using the given block