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: expander.go
    path of file: ./repos/kubernetes/pkg/volume/flexvolume
    
    the code of the file until where you have to start completion: /*
Copyright 2018 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the
    
func (plugin *flexVolumePlugin) NodeExpand(rsOpt volume.NodeResizeOptions) (bool, error) {
	// This method is called after we spec.PersistentVolume.Spec.Capacity
	// has been updated to the new size. The underlying driver thus sees
	// the _new_ (requested) size and can find out the _current_ size from
	// its underlying storage implementation

	if rsOpt.VolumeSpec.PersistentVolume == nil {
		return false, fmt.Errorf("PersistentVolume not found for spec: %s", rsOpt.VolumeSpec.Name())
	}

	call := plugin.NewDriverCall(expandFSCmd)
	call.AppendSpec(rsOpt.VolumeSpec, plugin.host, nil)
	call.Append(rsOpt.DevicePath)
	call.Append(rsOpt.DeviceMountPath)
	call.Append(strconv.FormatInt(rsOpt.NewSize.Value(), 10))
	call.Append(strconv.FormatInt(rsOpt.OldSize.Value(), 10))

	_, err := call.Run()
	if isCmdNotSupportedErr(err) {
		return newExpanderDefaults(plugin).NodeExpand(rsOpt)
	}
	if err != nil {
		return false, err
	}
	return true, nil
}