You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: wrr.go
    path of file: ./repos/sharingan/grpc-server/v1.33.2/xds/internal/testutils
    
    the code of the file until where you have to start completion: /*
 *
 * Copyright 2020 gRPC authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may no
    
func (twrr *testWRR) Add(item interface{}, weight int64) {
	twrr.itemsWithWeight = append(twrr.itemsWithWeight, struct {
		item   interface{}
		weight int64
	}{item: item, weight: weight})
	twrr.length++
}