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: enterprise_cert.go
    path of file: ./repos/moby/vendor/google.golang.org/api/internal/cert
    
    the code of the file until where you have to start completion: // Copyright 2022 Google LLC.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Package cert contains certificate tools for Google API clients.
// This package is intended to be used with c
    
func NewEnterpriseCertificateProxySource(configFilePath string) (Source, error) {
	key, err := client.Cred(configFilePath)
	if err != nil {
		if errors.Is(err, client.ErrCredUnavailable) {
			return nil, errSourceUnavailable
		}
		return nil, err
	}

	return (&ecpSource{
		key: key,
	}).getClientCertificate, nil
}