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: opendrive.go
    path of file: ./repos/rclone/backend/opendrive
    
    the code of the file until where you have to start completion: // Package opendrive provides an interface to the OpenDrive storage system.
package opendrive

import (
	"context"
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"path"
	"strconv"
	"strings"
	"time"

	"github.com/rclone/rclone/fs"
	"github.com/rclone/rclone/fs/config"
	"github.com/rclone/rclone/fs/config/configmap"
	"github.com/rclone/rclone/fs/config/configstruct"
	"github.com/rclone/rclone/fs/config/obscure"
	"github.com/rclone/rclone/fs/fserrors"
	"github.com/rclone/rclone/fs/fshttp"
	"github.com/rclone/rclone/fs/hash"
	"github.com/rclone/rclone/lib/dircache"
	"github.com/rclone/rclone/lib/encoder"
	"github.com/rclone/rclone/lib/pacer"
	"github.com/rclone/rclone/lib/readers"
	"github.com/rclone/rclone/lib/rest"
)

const (
	defaultEndpoint = "https://dev.opendrive.com/api/v1"
	minSleep        = 10 * time.Millisecond
	maxSleep        = 5 * time.Minute
	decayConstant   = 1 // bigger for slower decay, exponential
)

// Register with Fs
func init() {
	fs.Register(&fs.RegInfo{
		Name:        "opendrive",
		Description: "OpenDrive",
		NewFs:       NewFs,
		Options: []fs.Option{{
			Name:      "username",
			Help:      "Username.",
			Required:  true,
			Sensitive: true,
		}, {
			Name:       "password",
			Help:       "Password.",
			IsPassword: true,
			Required:   true,
		}, {
			Name:     config.ConfigEncoding,
			Help:     config.ConfigEncodingHelp,
			Advanced: true,
			// List of replaced characters:
			//   < (less than)     -> '＜' // FULLWIDTH LESS-THAN SIGN
			//   > (greater than)  -> '＞' // FULLWIDTH GREATER-THAN SIGN
			//   : (colon)         -> '：' // FULLWIDTH COLO
    
func NewFs(ctx context.Context, name, root string, m configmap.Mapper) (fs.Fs, error) {
	// Parse config into Options struct
	opt := new(Options)
	err := configstruct.Set(m, opt)
	if err != nil {
		return nil, err
	}
	root = parsePath(root)
	if opt.UserName == "" {
		return nil, errors.New("username not found")
	}
	opt.Password, err = obscure.Reveal(opt.Password)
	if err != nil {
		return nil, errors.New("password could not revealed")
	}
	if opt.Password == "" {
		return nil, errors.New("password not found")
	}

	f := &Fs{
		name:  name,
		root:  root,
		opt:   *opt,
		srv:   rest.NewClient(fshttp.NewClient(ctx)).SetErrorHandler(errorHandler),
		pacer: fs.NewPacer(ctx, pacer.NewDefault(pacer.MinSleep(minSleep), pacer.MaxSleep(maxSleep), pacer.DecayConstant(decayConstant))),
	}

	f.dirCache = dircache.New(root, "0", f)

	// set the rootURL for the REST client
	f.srv.SetRoot(defaultEndpoint)

	// get sessionID
	var resp *http.Response
	err = f.pacer.Call(func() (bool, error) {
		account := Account{Username: opt.UserName, Password: opt.Password}

		opts := rest.Opts{
			Method: "POST",
			Path:   "/session/login.json",
		}
		resp, err = f.srv.CallJSON(ctx, &opts, &account, &f.session)
		return f.shouldRetry(ctx, resp, err)
	})
	if err != nil {
		return nil, fmt.Errorf("failed to create session: %w", err)
	}
	fs.Debugf(nil, "Starting OpenDrive session with ID: %s", f.session.SessionID)

	f.features = (&fs.Features{
		CaseInsensitive:         true,
		CanHaveEmptyDirectories: true,
	}).Fill(ctx, f)

	// Find the current root
	err = f.dirCache.FindRoot(ctx, false)
	if err != nil {
		// Assume it is a file
		newRoot, remote := dircache.SplitPath(root)
		tempF := *f
		tempF.dirCache = dircache.New(newRoot, "0", &tempF)
		tempF.root = newRoot

		// Make new Fs which is the parent
		err = tempF.dirCache.FindRoot(ctx, false)
		if err != nil {
			// No root so return old f
			return f, nil
		}
		_, err := tempF.newObjectWithInfo(ctx, remote, nil, "")
		if err != nil {
			if err == fs.ErrorObjectNotFound {
				// File doesn't exist so return old f
				return f, nil
			}
			return nil, err
		}
		// XXX: update the old f here instead of returning tempF, since
		// `features` were already filled with functions having *f as a receiver.
		// See https://github.com/rclone/rclone/issues/2182
		f.dirCache = tempF.dirCache
		f.root = tempF.root
		// return an error with an fs which points to the parent
		return f, fs.ErrorIsFile
	}
	return f, nil
}