Getting TypeError when using openai.files.create()

I’m trying to create a file via the assistant API a few different ways and getting an error: TypeError: Invalid value given to form, expected a string, number, boolean, object, Array, File or Blob but got function()

Here’s my code:

const response = await fetch(fileURL);
if (!response.ok) {
    throw `HTTP Response Code: ${response.status}`;
}

const arrayBuffer = await response.arrayBuffer(); 
const uint8Array = new Uint8Array(arrayBuffer);
const readableStream = Readable.from(uint8Array);

const selection = await openai.files.create({
    file: readableStream,
    purpose: "assistants",
});

I’m not sure how to get the file from the URL to the API; what am I doing wrong here?

Thanks!