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: mode.go
    path of file: ./repos/goreportcard/vendor/honnef.co/go/tools/go/ir
    
    the code of the file until where you have to start completion: // Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package ir

// This file defines the BuilderMode type and its command-line flag.

import (
	"bytes"
    
func (m BuilderMode) String() string {
	var buf bytes.Buffer
	if m&GlobalDebug != 0 {
		buf.WriteByte('D')
	}
	if m&PrintPackages != 0 {
		buf.WriteByte('P')
	}
	if m&PrintFunctions != 0 {
		buf.WriteByte('F')
	}
	if m&PrintSource != 0 {
		buf.WriteByte('A')
	}
	if m&LogSource != 0 {
		buf.WriteByte('S')
	}
	if m&SanityCheckFunctions != 0 {
		buf.WriteByte('C')
	}
	if m&NaiveForm != 0 {
		buf.WriteByte('N')
	}
	return buf.String()
}