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: usage.go
    path of file: ./repos/jwx/jwk
    
    the code of the file until where you have to start completion: package jwk

import "fmt"

func (k KeyUsageType) String() string {
	return string(k)
}

func (k *KeyUsageType) Accept(v interface{}) error {
	switch v := v.(type) {
	case KeyUsageType:
		switch v {
		case ForSignature, ForEncryption:

    
func (k *KeyUsageType) Accept(v interface{}) error {
	switch v := v.(type) {
	case KeyUsageType:
		switch v {
		case ForSignature, ForEncryption:
			*k = v
			return nil
		default:
			return fmt.Errorf("invalid key usage type %s", v)
		}
	case string:
		switch v {
		case ForSignature.String(), ForEncryption.String():
			*k = KeyUsageType(v)
			return nil
		default:
			return fmt.Errorf("invalid key usage type %s", v)
		}
	}

	return fmt.Errorf("invalid value for key usage type %s", v)
}