Fetch fields from another DocType into a child table

frappe.ui.form.on("[PARENT_DOCTYPE_TARGET]", "refresh", function(frm) {
frappe.ui.form.on("[CHILD_TABLE_TARGET_DOCTYPE]", {
"[CHILD_TABLE_LINK FIELD]": function(frm) {
frm.add_fetch("[CHILD_TABLE_LINK FIELD]", "[SOURCE_CUSTOM_FIELD2]", "[TARGET_CUSTOM_FIELD2]");
}
});

});