constructor(responseMessage, methodDescriptor, metadata = {}, status = null) {
    /**
     * @const {RESPONSE}
     * @private
     */
    this.responseMessage_ = responseMessage;

    /**
     * @const {!Metadata}
     * @private
     */
    this.metadata_ = metadata;

    /**
     * @const {!MethodDescriptor<REQUEST, RESPONSE>}
     * @private
     */
    this.methodDescriptor_ = methodDescriptor;

    /**
     * @const {?Status}
     * @private
     */
    this.status_ = status;
  }
@param {RESPONSE} responseMessage
@param {!MethodDescriptor<REQUEST, RESPONSE>} methodDescriptor
@param {!Metadata=} metadata
@param {?Status=} status