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: mountstats.go
    path of file: ./repos/plumber/vendor/github.com/prometheus/procfs
    
    the code of the file until where you have to start completion: // Copyright 2018 The Prometheus Authors
// 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
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writi
    
func parseMountStats(r io.Reader) ([]*Mount, error) {
	const (
		device            = "device"
		statVersionPrefix = "statvers="

		nfs3Type = "nfs"
		nfs4Type = "nfs4"
	)

	var mounts []*Mount

	s := bufio.NewScanner(r)
	for s.Scan() {
		// Only look for device entries in this function
		ss := strings.Fields(string(s.Bytes()))
		if len(ss) == 0 || ss[0] != device {
			continue
		}

		m, err := parseMount(ss)
		if err != nil {
			return nil, err
		}

		// Does this mount also possess statistics information?
		if len(ss) > deviceEntryLen {
			// Only NFSv3 and v4 are supported for parsing statistics
			if m.Type != nfs3Type && m.Type != nfs4Type {
				return nil, fmt.Errorf("cannot parse MountStats for fstype %q", m.Type)
			}

			statVersion := strings.TrimPrefix(ss[8], statVersionPrefix)

			stats, err := parseMountStatsNFS(s, statVersion)
			if err != nil {
				return nil, err
			}

			m.Stats = stats
		}

		mounts = append(mounts, m)
	}

	return mounts, s.Err()
}