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: change.go
    path of file: ./repos/go-git/utils/merkletrie
    
    the code of the file until where you have to start completion: package merkletrie

import (
	"fmt"
	"io"

	"github.com/go-git/go-git/v5/utils/merkletrie/noder"
)

// Action values represent the kind of things a Change can represent:
// insertion, deletio
    
func (c *Change) Action() (Action, error) {
	if c.From == nil && c.To == nil {
		return Action(0), fmt.Errorf("malformed change: nil from and to")
	}
	if c.From == nil {
		return Insert, nil
	}
	if c.To == nil {
		return Delete, nil
	}

	return Modify, nil
}