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: spanner_list_backups.go
    path of file: ./repos/golang-samples/spanner/spanner_snippets/spanner
    
    the code of the file until where you have to start completion: // Copyright 2020 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package spanner

// [START spanner_list_backups]

import (
	"context"
	"fmt"
	"io"
	"regexp"
	"time"

	database "cloud.google.com/go/spanner/admin/database/apiv1"
	"google.golang.org/api/iterator"
	adminpb "google.golang.org/genproto/googleapis/spanner/admin/database/v1"
)

func listBackups(ctx context.Context, w io.Writer, db, backupID string) error {
	adminClient, err := database.NewDatabaseAdminClient(ctx)
	if err != nil {
		return err
	}
	defer adminClient.Close()

	matches := regexp.MustCompile
    
func listBackups(ctx context.Context, w io.Writer, db, backupID string) error {
	adminClient, err := database.NewDatabaseAdminClient(ctx)
	if err != nil {
		return err
	}
	defer adminClient.Close()

	matches := regexp.MustCompile("^(.*)/databases/(.*)$").FindStringSubmatch(db)
	if matches == nil || len(matches) != 3 {
		return fmt.Errorf("Invalid database id %s", db)
	}
	instanceName := matches[1]

	printBackups := func(iter *database.BackupIterator) error {
		for {
			resp, err := iter.Next()
			if err == iterator.Done {
				return nil
			}
			if err != nil {
				return err
			}
			fmt.Fprintf(w, "Backup %s\n", resp.Name)
		}
	}

	var iter *database.BackupIterator
	var filter string
	// List all backups.
	iter = adminClient.ListBackups(ctx, &adminpb.ListBackupsRequest{
		Parent: instanceName,
	})
	if err := printBackups(iter); err != nil {
		return err
	}

	// List all backups that contain a name.
	iter = adminClient.ListBackups(ctx, &adminpb.ListBackupsRequest{
		Parent: instanceName,
		Filter: "name:" + backupID,
	})
	if err := printBackups(iter); err != nil {
		return err
	}

	// List all backups that expire before a timestamp.
	expireTime := time.Now().AddDate(0, 0, 30)
	filter = fmt.Sprintf(`expire_time < "%s"`, expireTime.Format(time.RFC3339))
	iter = adminClient.ListBackups(ctx, &adminpb.ListBackupsRequest{
		Parent: instanceName,
		Filter: filter,
	})
	if err := printBackups(iter); err != nil {
		return err
	}

	// List all backups for a database that contains a name.
	iter = adminClient.ListBackups(ctx, &adminpb.ListBackupsRequest{
		Parent: instanceName,
		Filter: "database:" + db,
	})
	if err := printBackups(iter); err != nil {
		return err
	}

	// List all backups with a size greater than some bytes.
	iter = adminClient.ListBackups(ctx, &adminpb.ListBackupsRequest{
		Parent: instanceName,
		Filter: "size_bytes > 100",
	})
	if err := printBackups(iter); err != nil {
		return err
	}

	// List backups that were created after a timestamp that are also ready.
	createTime := time.Now().AddDate(0, 0, -1)
	filter = fmt.Sprintf(
		`create_time >= "%s" AND state:READY`,
		createTime.Format(time.RFC3339),
	)
	iter = adminClient.ListBackups(ctx, &adminpb.ListBackupsRequest{
		Parent: instanceName,
		Filter: filter,
	})
	if err := printBackups(iter); err != nil {
		return err
	}

	// List backups with pagination.
	request := &adminpb.ListBackupsRequest{
		Parent:   instanceName,
		PageSize: 10,
	}
	for {
		iter = adminClient.ListBackups(ctx, request)
		if err := printBackups(iter); err != nil {
			return err
		}
		pageToken := iter.PageInfo().Token
		if pageToken == "" {
			break
		} else {
			request.PageToken = pageToken
		}
	}

	fmt.Fprintf(w, "Backups listed.\n")
	return nil
}