code: function createInstanceAsync(service_uuid, opts, callback) {
      assert.string(service_uuid, 'service_uuid');
      if (typeof (opts) === 'function') {
          callback = opts;
          opts = {};
      }
      assert.object(opts, 'opts');
      assert.func(callback, 'callback');
  
      opts.service_uuid = service_uuid;
  
      return (this.post('/instances?async=true', opts, callback));
  }
docs: Create an instance asynchronously
  
  @param {String} service_uuid: The UUID of the service for which to create
  an instance.
  @param {String} opts: Optional attributes per
  <https://mo.joyent.com/docs/sapi/master/#CreateInstance>
  @param {Function} callback: of the form f(err, instance).