    def parse(obj)
      if convertor.kind_of?(Symbol) || convertor.kind_of?(String)
        obj.send(convertor)
      elsif convertor.kind_of?(Class)
        convertor.new(obj)
      elsif convertor.respond_to?(:call)
        if convertor.arity == 1
          convertor.call(obj)
        elsif convertor.arity == 0
          convertor.call
        else
          convertor.call(obj,self)
        end
      else
        "dunno how to convert"
      end
    end