code: function(schema, from) {
      return function(next) {
          var self = this;
          var funcs = [];
      
          for (var key in from) {
              var items = from[key];
              var model = mongoose.model(schema.path(key).options.ref);
          
              funcs.push(function(callback) {
                  model.findOne({ _id: self[key] }, function(err, instance) {
                      if (err) return callback(err);
                  
                      items.forEach(function(item) {
                          self[item.key] = instance[item.field];
                      });
                  
                      callback();
                  });
              });
          }
      
          async.parallel(funcs, function(err) {
              if (err) return next(err);
              next();
          });
      };
  }
docs: Denormalize values from foreign refs into local model