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: transform.go
    path of file: ./repos/hugo/resources/resource_transformers/tocss/dartsass
    
    the code of the file until where you have to start completion: // Copyright 2024 The Hugo Authors. All rights reserved.
//
// 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
// h
    
func (t importResolver) CanonicalizeURL(url string) (string, error) {
	if url == sass.HugoVarsNamespace {
		return url, nil
	}

	filePath, isURL := paths.UrlToFilename(url)
	var prevDir string
	var pathDir string
	if isURL {
		var found bool
		prevDir, found = t.c.sfs.MakePathRelative(filepath.Dir(filePath), true)

		if !found {
			// Not a member of this filesystem, let Dart Sass handle it.
			return "", nil
		}
	} else {
		prevDir = t.baseDir
		pathDir = path.Dir(url)
	}

	basePath := filepath.Join(prevDir, pathDir)
	name := filepath.Base(filePath)

	// Pick the first match.
	var namePatterns []string
	if strings.Contains(name, ".") {
		namePatterns = []string{"_%s", "%s"}
	} else if strings.HasPrefix(name, "_") {
		namePatterns = []string{"_%s.scss", "_%s.sass", "_%s.css"}
	} else {
		namePatterns = []string{"_%s.scss", "%s.scss", "_%s.sass", "%s.sass", "_%s.css", "%s.css"}
	}

	name = strings.TrimPrefix(name, "_")

	for _, namePattern := range namePatterns {
		filenameToCheck := filepath.Join(basePath, fmt.Sprintf(namePattern, name))
		fi, err := t.c.sfs.Fs.Stat(filenameToCheck)
		if err == nil {
			if fim, ok := fi.(hugofs.FileMetaInfo); ok {
				t.dependencyManager.AddIdentity(identity.CleanStringIdentity(filenameToCheck))
				return "file://" + filepath.ToSlash(fim.Meta().Filename), nil
			}
		}
	}

	// Not found, let Dart Dass handle it
	return "", nil
}