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: mapMorphism.go
    path of file: ./repos/sealer/vendor/github.com/polydawn/refmt/obj/atlas
    
    the code of the file until where you have to start completion: package atlas

import (
	"fmt"
	"reflect"
)

type MapMorphism struct {
	KeySortMode KeySortMode
}

func (x *BuilderCore) MapMorphism() *BuilderMapMorphism {
	if x.entry.Type.Kind() != reflect.Map {
		panic(fmt.Errorf("cannot use mapMorphism for type 
    
func (x *BuilderCore) MapMorphism() *BuilderMapMorphism {
	if x.entry.Type.Kind() != reflect.Map {
		panic(fmt.Errorf("cannot use mapMorphism for type %q, which is kind %s", x.entry.Type, x.entry.Type.Kind()))
	}
	x.entry.MapMorphism = &MapMorphism{
		KeySortMode_Default,
	}
	return &BuilderMapMorphism{x.entry}
}