Is there a issue in calling frm,add_child() from on_submit(frm)

on_submit(frm){
frappe.db.get_doc(‘Customer’, null, { customer_name: frm.doc.farmer_name }).then(doc => {
frappe.model.set_value(frm.doctype,frm.docname, “farmer_customer_link”, doc.name);
>>>>>var new_row = frm.add_child(‘links’, {link_doctype : ‘Customer’, link_name : frm.doc.farmer_customer_link});
frm.refresh_field(“links”);
});
Adding this call frm.add_child … script error is reported

image

Any help appreciated