frm.add_custom_button(__('New Tasks'), function() {
frappe.prompt([
{'label': 'Assigned To', 'fieldname': 'assigned_to', 'fieldtype': 'Link', 'options': 'Employee'},
{fieldtype: 'Column Break',},
{'label': 'User ID','fieldname': 'user_id','fieldtype': 'Data','fetch_from': 'assigned_to.user_id','options':'User'},
], function(values){
console.log('userr',values.user_id);
why this user_id not getting fetched