Updating options in select field in child table

Hi

I am trying to modify the select options of the content_type field in the topic_content
child table of the Topic doc.

I am looking at this posting …

https://discuss.frappe.io/t/set-the-options-for-a-select-field-in-a-child-doctype-using-serverside-script/108480/5

but if I apply the info from this post and try …

frappe.ui.form.on('Topic', {
	refresh(frm) {
	    let fields=["val1", "val2"];
	    debugger;
        frm.fields_dict.topic_content.grid.update_docfield_property(
            “content_type”,
            “options”,
            [“”].concat(fields)
        );		
	}
});

it doesn’t even get to the debugger statement …

setup@https://<domain>/assets/frappe/dist/js/form.bundle.SZI4GDIZ.js:180:15
setup@https://<domain>/assets/frappe/dist/js/form.bundle.SZI4GDIZ.js:5819:27
refresh@https://<domain>/assets/frappe/dist/js/form.bundle.SZI4GDIZ.js:6063:16
render@https://<domain>/assets/frappe/dist/js/form.bundle.SZI4GDIZ.js:967:49
show_doc@https://<domain>/assets/frappe/dist/js/form.bundle.SZI4GDIZ.js:936:14
make_and_show@https://<domain>/assets/frappe/dist/js/form.bundle.SZI4GDIZ.js:907:14
make/<@https://<domain>/assets/frappe/dist/js/form.bundle.SZI4GDIZ.js:892:16
with_doctype@https://<domain>/assets/frappe/dist/js/desk.bundle.ACFWVWJS.js:2046:25
make@https://<domain>/assets/frappe/dist/js/form.bundle.SZI4GDIZ.js:889:22
show@https://<domain>/assets/frappe/dist/js/desk.bundle.ACFWVWJS.js:48801:16
render_page@https://<domain>/assets/frappe/dist/js/desk.bundle.ACFWVWJS.js:38569:38
render@https://<domain>/assets/frappe/dist/js/desk.bundle.ACFWVWJS.js:38556:14
route@https://<domain>/assets/frappe/dist/js/desk.bundle.ACFWVWJS.js:38463:12
async*push_state@https://<domain>/assets/frappe/dist/js/desk.bundle.ACFWVWJS.js:38685:14
set_route/<@https://<domain>/assets/frappe/dist/js/desk.bundle.ACFWVWJS.js:38606:16
set_route@https://<domain>/assets/frappe/dist/js/desk.bundle.ACFWVWJS.js:38595:14
frappe.set_route@https://<domain>/assets/frappe/dist/js/desk.bundle.ACFWVWJS.js:38749:36
open_doc@https://<domain>/assets/frappe/dist/js/form.bundle.SZI4GDIZ.js:1200:14
render_edit_in_full_page_link/<@https://<domain>/assets/frappe/dist/js/form.bundle.SZI4GDIZ.js:1204:69
dispatch@https://<domain>/assets/frappe/dist/js/libs.bundle.6XLVBACU.js:2802:105
node_modules/jquery/dist/jquery.js/

What am I doing wrong in applying the info from the post. Please help.

Reference:

Thank you @NCP . Let me work through that post.
Also, thank you for sharing your coding experience on your youtube channel