DS.AdapterError.extend fails

based on documentation http://ift.tt/2p9DmXQ I am trying to duplicate.

my code :

  import DS from 'ember-data';

  export default DS.AdapterError.extend({ message: "Down for maintenance." });

but I just get errors

Uncaught TypeError: _emberData.default.AdapterError.extend is not a function

has anyone extended this error object? I ma truly just capturing 401,403 errors that happen during the ember-data transaction. I wanted to use some custom errors.