code: function request(svc, operation, params, next, extra) {
      var world = this;
  
      if (!svc) svc = this.service;
      if (typeof svc === 'string') svc = this[svc];
  
      svc[operation](params, function(err, data) {
        world.response = this;
        world.error = err;
        world.data = data;
  
        try {
          if (typeof next.condition === 'function') {
            var condition = next.condition.call(world, world);
            if (!condition) {
              next.fail(new Error('Request success condition failed'));
              return;
            }
          }
  
          if (extra) {
            extra.call(world, world.response);
            next.call(world);
          }
          else if (extra !== false && err) {
            world.unexpectedError(world.response, next);
          } else {
            next.call(world);
          }
        } catch (err) {
          next.fail(err);
        }
      });
    }
docs: A short-cut for calling a service operation and waiting for it to
  finish execution before moving onto the next step in the scenario.