add column to tickets-list.php

/*
Add new column in the ticket list table under Booking Form at Single Events Page

Part 2 -> http://pastebin.com/LdjxXzCW
       -> create the template folder/file at plugin-templates/events-manager/forms/bookingform/tickets-list.php

*/
function my_em_mod_add_ticket_column( $collumns, $EM_Event ){
 $collumns['available_spaces'] = __('Available Spaces','dbem');
 return $collumns;
}
add_filter('em_booking_form_tickets_cols', 'my_em_mod_add_ticket_column',10,2);