sign({
    requestPath,
    method,
    isoTimestamp,
    data,
  }: {
    requestPath: string,
    method: RequestMethod,
    isoTimestamp: ISO8601,
    data?: {},
  }): string {
    const messageString: string = (
      isoTimestamp +
      METHOD_ENUM_MAP[method] +
      requestPath +
      (_.isEmpty(data) ? '' : JSON.stringify(data))
    );

    return crypto.createHmac(
      'sha256',
      Buffer.from(this.apiKeyCredentials.secret, 'base64'),
    ).update(messageString).digest('base64');
  }