How to use the @sindresorhus/is.undefined function in @sindresorhus/is

if ((opts.form || opts.json) && !canBodyBeStringified) {
			throw new TypeError('The `body` option must be a plain Object or Array when the `form` or `json` option is used');
		}

		if (isFormData(body)) {
			// Special case for https://github.com/form-data/form-data
			headers['content-type'] = headers['content-type'] || `multipart/form-data; boundary=${body.getBoundary()}`;
		} else if (opts.form && canBodyBeStringified) {
			headers['content-type'] = headers['content-type'] || 'application/x-www-form-urlencoded';
			opts.body = querystring.stringify(body);
		} else if (opts.json && canBodyBeStringified) {
			headers['content-type'] = headers['content-type'] || 'application/json';
			opts.body = JSON.stringify(body);
		}

		if (is.undefined(headers['content-length']) && is.undefined(headers['transfer-encoding']) && !is.nodeStream(body)) {
			const length = is.string(opts.body) ? Buffer.byteLength(opts.body) : opts.body.length;
			headers['content-length'] = length;
		}

		// Convert buffer to stream to receive upload progress events
		// see https://github.com/sindresorhus/got/pull/322
		if (is.buffer(body)) {
			opts.body = intoStream(body);
			opts.body._buffer = body;
		}

		opts.method = (opts.method || 'POST').toUpperCase();
	}

	if (opts.hostname === 'unix') {
		const matches = /(.+?):(.+)/.exec(opts.path);

export const isVoiceMessage = (attachment: Attachment): boolean => {
  const flag = SignalService.AttachmentPointer.Flags.VOICE_MESSAGE;
  const hasFlag =
    // tslint:disable-next-line no-bitwise
    !is.undefined(attachment.flags) && (attachment.flags & flag) === flag;
  if (hasFlag) {
    return true;
  }

  const isLegacyAndroidVoiceMessage =
    !is.undefined(attachment.contentType) &&
    MIME.isAudio(attachment.contentType) &&
    !attachment.fileName;
  if (isLegacyAndroidVoiceMessage) {
    return true;
  }

  return false;
};

export const isVoiceMessage = (attachment: Attachment): boolean => {
  const flag = SignalService.AttachmentPointer.Flags.VOICE_MESSAGE;
  const hasFlag =
    // tslint:disable-next-line no-bitwise
    !is.undefined(attachment.flags) && (attachment.flags & flag) === flag;
  if (hasFlag) {
    return true;
  }

  const isLegacyAndroidVoiceMessage =
    !is.undefined(attachment.contentType) &&
    MIME.isAudio(attachment.contentType) &&
    !attachment.fileName;
  if (isLegacyAndroidVoiceMessage) {
    return true;
  }

  return false;
};

export default function merge, Source extends Record>(target: Target, ...sources: Source[]): Target & Source {
	for (const source of sources) {
		for (const [key, sourceValue] of Object.entries(source)) {
			if (is.undefined(sourceValue)) {
				continue;
			}

			const targetValue = target[key];
			if (targetValue instanceof URLSearchParams && sourceValue instanceof URLSearchParams) {
				const params = new URLSearchParams();

				const append = (value: string, key: string): void => params.append(key, value);
				targetValue.forEach(append);
				sourceValue.forEach(append);

				// @ts-ignore https://github.com/microsoft/TypeScript/issues/31661
				target[key] = params;
			} else if (is.urlInstance(targetValue) && (is.urlInstance(sourceValue) || is.string(sourceValue))) {
				// @ts-ignore
				target[key] = new URL(sourceValue as string, targetValue);

options.body = toReadableStream(options.body!);
	}

	// See https://tools.ietf.org/html/rfc7230#section-3.3.2
	// A user agent SHOULD send a Content-Length in a request message when
	// no Transfer-Encoding is sent and the request method defines a meaning
	// for an enclosed payload body.  For example, a Content-Length header
	// field is normally sent in a POST request even when the value is 0
	// (indicating an empty payload body).  A user agent SHOULD NOT send a
	// Content-Length header field when the request message does not contain
	// a payload body and the method semantics do not anticipate such a
	// body.
	if (is.undefined(headers['content-length']) && is.undefined(headers['transfer-encoding'])) {
		if (
			(options.method === 'POST' || options.method === 'PUT' || options.method === 'PATCH') &&
			!is.undefined(uploadBodySize)
		) {
			// @ts-ignore We assign if it is undefined, so this IS correct
			headers['content-length'] = String(uploadBodySize);
		}
	}

	if (!options.isStream && options.responseType === 'json' && is.undefined(headers.accept)) {
		headers.accept = 'application/json';
	}

	if (options.decompress && is.undefined(headers['accept-encoding'])) {
		headers['accept-encoding'] = supportsBrotli ? 'gzip, deflate, br' : 'gzip, deflate';
	}

	// Validate URL
	if (options.url.protocol !== 'http:' && options.url.protocol !== 'https:') {

if (opts.decompress && is.undefined(opts.headers['accept-encoding'])) {
		opts.headers['accept-encoding'] = 'gzip, deflate';
	}

	const query = opts.query;

	if (query) {
		if (!is.string(query)) {
			opts.query = querystring.stringify(query);
		}

		opts.path = `${opts.path.split('?')[0]}?${opts.query}`;
		delete opts.query;
	}

	if (opts.json && is.undefined(opts.headers.accept)) {
		opts.headers.accept = 'application/json';
	}

	const body = opts.body;
	if (is.nullOrUndefined(body)) {
		opts.method = (opts.method || 'GET').toUpperCase();
	} else {
		const headers = opts.headers;
		if (!is.nodeStream(body) && !is.string(body) && !is.buffer(body) && !(opts.form || opts.json)) {
			throw new TypeError('The `body` option must be a stream.Readable, string, Buffer or plain Object');
		}

		const canBodyBeStringified = is.plainObject(body) || is.array(body);
		if ((opts.form || opts.json) && !canBodyBeStringified) {
			throw new TypeError('The `body` option must be a plain Object or Array when the `form` or `json` option is used');
		}

},
		opts
	);

	const headers = lowercaseKeys(opts.headers);
	for (const key of Object.keys(headers)) {
		if (is.nullOrUndefined(headers[key])) {
			delete headers[key];
		}
	}

	opts.headers = Object.assign({
		'user-agent': `${pkg.name}/${pkg.version} (https://github.com/sindresorhus/got)`
	}, headers);

	if (opts.decompress && is.undefined(opts.headers['accept-encoding'])) {
		opts.headers['accept-encoding'] = 'gzip, deflate';
	}

	const query = opts.query;

	if (query) {
		if (!is.string(query)) {
			opts.query = querystring.stringify(query);
		}

		opts.path = `${opts.path.split('?')[0]}?${opts.query}`;
		delete opts.query;
	}

	if (opts.json && is.undefined(opts.headers.accept)) {
		opts.headers.accept = 'application/json';

formatTrace(
    { stack, queue, currentAction },
    max = FFlatPrettyPrinter.consoleWidth
  ): string {
    const maxOutputWidth =
      this.opts.maxOutputLength || FFlatPrettyPrinter.consoleWidth;
    max = max < 0 ? maxOutputWidth / 2 + max : max / 2;
    max -= 16;

    const stackString = this.formatArray(stack, 0);
    const lastActionString = is.undefined(currentAction)
      ? ''
      : this.formatValue(currentAction, 0);
    const queueString = this.formatArray(queue, 0);
    return `${lpad(stackString, max)}> ${fixedWidthString(
      lastActionString,
      16
    )} <${rtrim(queueString, max)}`;
  }

if (!is.function(opts.retries)) {
		const retries = opts.retries;

		opts.retries = (iter, err) => {
			if (iter > retries || !isRetryAllowed(err)) {
				return 0;
			}

			const noise = Math.random() * 100;

			return ((1 << iter) * 1000) + noise;
		};
	}

	if (is.undefined(opts.followRedirect)) {
		opts.followRedirect = true;
	}

	if (opts.timeout) {
		if (is.number(opts.timeout)) {
			opts.gotTimeout = {request: opts.timeout};
		} else {
			opts.gotTimeout = opts.timeout;
		}
		delete opts.timeout;
	}

	return opts;
}

};
		}
	}

	const {headers} = options;
	for (const [key, value] of Object.entries(headers)) {
		if (is.nullOrUndefined(value)) {
			delete headers[key];
		}
	}

	if (options.json && is.undefined(headers.accept)) {
		headers.accept = 'application/json';
	}

	if (options.decompress && is.undefined(headers['accept-encoding'])) {
		headers['accept-encoding'] = 'gzip, deflate';
	}

	const {body} = options;
	if (is.nullOrUndefined(body)) {
		options.method = options.method ? options.method.toUpperCase() : 'GET';
	} else {
		const isObject = is.object(body) && !is.buffer(body) && !is.nodeStream(body);
		if (!is.nodeStream(body) && !is.string(body) && !is.buffer(body) && !(options.form || options.json)) {
			throw new TypeError('The `body` option must be a stream.Readable, string or Buffer');
		}

		if (options.json && !(isObject || is.array(body))) {
			throw new TypeError('The `body` option must be an Object or Array when the `json` option is used');
		}