func IsMessageSet(md pref.MessageDescriptor) bool {
	xmd, ok := md.(interface{ IsMessageSet() bool })
	return ok && xmd.IsMessageSet()
}
IsMessageSet returns whether the message uses the MessageSet wire format.
package messageset
import (
	"math"
	"google.golang.org/protobuf/encoding/protowire"
	"google.golang.org/protobuf/internal/errors"
	pref "google.golang.org/protobuf/reflect/protoreflect"
	preg "google.golang.org/protobuf/reflect/protoregistry"
)
const (
	FieldItem    = protowire.Number(1)
	FieldTypeID  = protowire.Number(2)
	FieldMessage = protowire.Number(3)
)
const ExtensionName = "message_set_extension"