Node.js on AWS Lambda: UnstructuredLoader in LangChain Throws ENOENT Error with Valid API Key

Question

I'm encountering a challenging issue with the UnstructuredLoader from the LangChain library in a Node.js application running on AWS Lambda. Despite providing a valid API key, the loader throws an ENOENT error, indicating an invalid API key.

Here's the error log:

2023-12-05T14:20:10.745Z    9482936f-6dd0-5bc7-99ce-ce865e1eb340    ERROR   Invoke Error    {
    "errorType": "Error",
    "errorMessage": "Failed to partition file /tmp/README.md with error 401 and message {\"detail\":\"API key is invalid, please provide a valid API key in the header.\"}",
    "stack": [
        "Error: Failed to partition file /tmp/README.md with error 401 and message {\"detail\":\"API key is invalid, please provide a valid API key in the header.\"}",
        "    at UnstructuredLoader._partition (/var/task/node_modules/langchain/dist/document_loaders/fs/unstructured.cjs:189:19)",
        "    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)",
        "    at async UnstructuredLoader.load (/var/task/node_modules/langchain/dist/document_loaders/fs/unstructured.cjs:198:26)",
        "    at async processFile (/var/task/index.js:103:21)",
        "    at async Runtime.handler (/var/task/index.js:151:5)"
    ]
}

The issue arises specifically when using the UnstructuredLoader for processing file types that are not natively supported by other loaders in LangChain (e.g., PPTX files). I have confirmed that the API key is correctly set in the environment variables and works fine for other loaders.

Here's a relevant snippet of the implementation:

async function processFile(filename: string, key: string) {
  try {
    // Fetch the File content from S3 using the new method
    const command = new GetObjectCommand({
      Bucket: process.env.S3_BUCKET_NAME,
      Key: filename,
    });
    const content: any = await s3Client.send(command);

    const tempFilePath = path.join('/tmp', path.basename(filename));
    await fs.writeFile(tempFilePath, content.Body); // Directly save the buffer

    // Load and split the File
    const fileExtension = path.extname(tempFilePath).toLowerCase();
    let loader: any;
    switch (fileExtension) {
      ...
      default:
        loader = new UnstructuredLoader(tempFilePath, { apiKey: key });
    }
    ...
  } catch (error) {
    console.error(`Error processing and ingesting File: ${filename}. Error: ${error}`);
    throw error;
  }
}

I've ensured that the API key is being passed correctly to the UnstructuredLoader. This setup works flawlessly for other file types but not for those requiring the UnstructuredLoader. Is there something I'm missing in the configuration or usage of the UnstructuredLoader? Any insights or experiences with similar issues would be immensely helpful.