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: login.go
    path of file: ./repos/vault/command
    
    the code of the file until where you have to start completion: // Copyright (c) HashiCorp, Inc.
// SPDX-License-Identifier: BUSL-1.1

package command

import (
	"fmt"
	"io"
	"os"
	"strings"

	"github.com/hashicorp/vault/api"
	"github.com/posener/complete"
)

// LoginHandler is the interface that any auth handlers must implement to enable
// auth via the CLI.
type LoginHandler interface {
	Auth(*api.Client, 
    
func (c *LoginCommand) extractToken(client *api.Client, secret *api.Secret, unwrap bool) (*api.Secret, bool, error) {
	switch {
	case secret == nil:
		return nil, false, fmt.Errorf("empty response from auth helper")

	case secret.Auth != nil:
		return secret, false, nil

	case secret.WrapInfo != nil:
		if secret.WrapInfo.WrappedAccessor == "" {
			return nil, false, fmt.Errorf("wrapped response does not contain a token")
		}

		if !unwrap {
			return secret, true, nil
		}

		client.SetToken(secret.WrapInfo.Token)
		secret, err := client.Logical().Unwrap("")
		if err != nil {
			return nil, false, err
		}
		return c.extractToken(client, secret, unwrap)

	default:
		return nil, false, fmt.Errorf("no auth or wrapping info in response")
	}
}