Error with Webform variables: Converting circular structure to JSON

I am trying to pass a variable from a in my custom app. I created the webform on desk and I am using only the myapp.mywebform files (py and js) created by desk.
My py code prints correctly on console:

import frappe

def get_context(context):
	context.user = frappe.session.user
	student_name = frappe.db.sql("""select student_name from `tabStudent` where user = %s""", (context.user))
	context.student_name = student_name[0][0]

My js code is

frappe.ready(() => {
    // bind events here
    frappe.web_form.after_load = setTimeout(function() {'get_context', self).then(r => {
            student = r.message;
            frappe.web_form.set_value('student_ce', student);

    }, 2000); // 2 seconds delay

No error messages appear on console (development mode, bench start running).
My browser console shows the following error and does not populate the student name (data fieldtype).

Any ideas? The student name prints with no extra characters, e.g.,
Paul Klee

bench 5.22.3, frappe 15.18.2, erpnext 15.17.5

I appreciate any help!