func CheckCodec(c Codec, internalType Object, externalTypes ...unversioned.GroupVersionKind) error {
	_, err := Encode(c, internalType)
	if err != nil {
		return fmt.Errorf("Internal type not encodable: %v", err)
	}
	for _, et := range externalTypes {
		exBytes := []byte(fmt.Sprintf(`{"kind":"%v","apiVersion":"%v"}`, et.Kind, et.GroupVersion().String()))
		obj, err := Decode(c, exBytes)
		if err != nil {
			return fmt.Errorf("external type %s not interpretable: %v", et, err)
		}
		if reflect.TypeOf(obj) != reflect.TypeOf(internalType) {
			return fmt.Errorf("decode of external type %s produced: %#v", et, obj)
		}
		err = DecodeInto(c, exBytes, internalType)
		if err != nil {
			return fmt.Errorf("external type %s not convertable to internal type: %v", et, err)
		}
	}
	return nil
}
CheckCodec makes sure that the codec can encode objects like internalType,
decode all of the external types listed, and also decode them into the given
object. (Will modify internalObject.) (Assumes JSON serialization.)
TODO: verify that the correct external version is chosen on encode...
package runtime
import (
	"fmt"
	"reflect"
	"k8s.io/kubernetes/pkg/api/unversioned"
)