code: func MustMarshalJSON(x interface{}) []byte {
  	bs, err := json.Marshal(x)
  	if err != nil {
  		panic(err)
  	}
  	return bs
  }
docs: // MustMarshalJSON returns the JSON encoding of x
  //
  // If the data cannot be encoded, this function will panic. This function is for
  // test purposes.