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: dev.go
    path of file: ./repos/gdu/pkg/device
    
    the code of the file until where you have to start completion: package device

import "strings"

// Device struct
type Device struct {
	Name       string
	MountPoint string
	Fstype     string
	Size       int64
	Free       int64
}

// GetUsage returns used size of device
func (d Device) GetUsage() int64 {
	return d.Size - d.Fre
    
func GetNestedMountpointsPaths(path string, mounts Devices) []string {
	paths := make([]string, 0, len(mounts))

	for _, mount := range mounts {
		if strings.HasPrefix(mount.MountPoint, path) && mount.MountPoint != path {
			paths = append(paths, mount.MountPoint)
		}
	}
	return paths
}