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: serviceconfig.go
    path of file: ./repos/agones/vendor/google.golang.org/grpc/internal/serviceconfig
    
    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 not use this file except in compliance 
    
func (bc *BalancerConfig) UnmarshalJSON(b []byte) error {
	var ir intermediateBalancerConfig
	err := json.Unmarshal(b, &ir)
	if err != nil {
		return err
	}

	var names []string
	for i, lbcfg := range ir {
		if len(lbcfg) != 1 {
			return fmt.Errorf("invalid loadBalancingConfig: entry %v does not contain exactly 1 policy/config pair: %q", i, lbcfg)
		}

		var (
			name    string
			jsonCfg json.RawMessage
		)
		// Get the key:value pair from the map. We have already made sure that
		// the map contains a single entry.
		for name, jsonCfg = range lbcfg {
		}

		names = append(names, name)
		builder := balancer.Get(name)
		if builder == nil {
			// If the balancer is not registered, move on to the next config.
			// This is not an error.
			continue
		}
		bc.Name = name

		parser, ok := builder.(balancer.ConfigParser)
		if !ok {
			if string(jsonCfg) != "{}" {
				logger.Warningf("non-empty balancer configuration %q, but balancer does not implement ParseConfig", string(jsonCfg))
			}
			// Stop at this, though the builder doesn't support parsing config.
			return nil
		}

		cfg, err := parser.ParseConfig(jsonCfg)
		if err != nil {
			return fmt.Errorf("error parsing loadBalancingConfig for policy %q: %v", name, err)
		}
		bc.Config = cfg
		return nil
	}
	// This is reached when the for loop iterates over all entries, but didn't
	// return. This means we had a loadBalancingConfig slice but did not
	// encounter a registered policy. The config is considered invalid in this
	// case.
	return fmt.Errorf("invalid loadBalancingConfig: no supported policies found in %v", names)
}