Send page fields to py of a Script Report

ERPNext Reports
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1

Hello everyone. I created a Script Report and added a Custom Field (an Attach button) with the Page API. I want to call the Execute function when the text file upload finishes (or any other function) of the py of the report. How can I send the file to the py?

Here is my js code.

frappe.query_reports["my report"] = {
    onload: function(report) {
        report.page.add_field({
            label: __("Attach"),
            fieldtype: "Attach",
            fieldname: "Attach"
        });
    }
}

I tried using filters parameter, but it sends the file into URL resulting in a long URL if the file has a lot of information. Any idea? I appreciate any help.