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: gdch.go
    path of file: ./repos/google-cloud-go/auth/detect/internal/gdch
    
    the code of the file until where you have to start completion: // Copyright 2023 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with th
    
func NewTokenProvider(f *internaldetect.GDCHServiceAccountFile, o *Options) (auth.TokenProvider, error) {
	if !gdchSupportFormatVersions[f.FormatVersion] {
		return nil, fmt.Errorf("detect: unsupported gdch_service_account format %q", f.FormatVersion)
	}
	if o.STSAudience == "" {
		return nil, errors.New("detect: STSAudience must be set for the GDCH auth flows")
	}
	pk, err := internal.ParseKey([]byte(f.PrivateKey))
	if err != nil {
		return nil, err
	}
	certPool, err := loadCertPool(f.CertPath)
	if err != nil {
		return nil, err
	}

	tp := gdchProvider{
		serviceIdentity: fmt.Sprintf("system:serviceaccount:%s:%s", f.Project, f.Name),
		tokenURL:        f.TokenURL,
		aud:             o.STSAudience,
		pk:              pk,
		pkID:            f.PrivateKeyID,
		certPool:        certPool,
		client:          o.Client,
	}
	return tp, nil
}