def dump(arg)
      if arg.instance_of? String
        File.open(arg, "w") {|f| YAML.dump(self, f) }
      else
        YAML.dump(arg)
      end
    end
def dump(arg)
      if arg.instance_of? String
        File.open(arg, "w") {|f| YAML.dump(self, f) }
      else
        YAML.dump(arg)
      end
    end
Dumps class instance to a data file (e.g., yaml) or a string