How to pass object from JS to eel? Or does eel only support string?

Question

Python

How to pass object from js to eel?
I am trying to export the result of js code.
Sample code from three.js
js

//TEXT
  let exporter_stl = new STLExporter();
    function exportASCII_stl() {
    const result = exporter_stl.parse( scene );
    console.log(result)
    let res = await eel.test_link(result,'stl')();
    }
  //Binary
    function exportBinary_stl() {
    const result = exporter_stl.parse( scene, { binary: true } );
    console.log(result)
    eel(result,'stl');
    let res = await eel.test_link(result,'stl')();
    }
  setTimeout(exportBinary_stl, 3000);

python

@eel.expose
  def test_link(content,format):
    print(content)
    file = open('test.'+format, 'w+')
    file.write(content)
    file.close()

But the problem is that exportBinary_stl returns me an empty {}
And in the console itself, it returns

js

python


typeof showed that the data type that I want to pass is called object

For comparison, exportASCII_stl returns everything correctly in both consoles.
typeof showed that it is a string

js

python


I don't understand how I can pass the Binary code.
When I open it in a text editor, I get an unidentified code.
When I tried to generate a link and follow it in the browser, the file downloaded immediately. without being able to see its code.
I waited for the entire code to load, but I still get empty parentheses.
Has anyone passed the Binary code before. Object or Image.
Or does eel only support sring or number?