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: bflag.go
    path of file: ./repos/moby/vendor/github.com/moby/buildkit/frontend/dockerfile/instructions
    
    the code of the file until where you have to start completion: package instructions

import (
	"strings"

	"github.com/moby/buildkit/util/suggest"
	"github.com/pkg/errors"
)

// FlagType is the type of the build flag
type FlagType int

c
    
func (bf *BFlags) addFlag(name string, flagType FlagType) *Flag {
	if _, ok := bf.flags[name]; ok {
		bf.Err = errors.Errorf("Duplicate flag defined: %s", name)
		return nil
	}

	newFlag := &Flag{
		bf:       bf,
		name:     name,
		flagType: flagType,
	}
	bf.flags[name] = newFlag

	return newFlag
}