protected function set_up($args)
 {
     $db = new Database($this->wpdb);
     $this->table = $db->get_table($args['table']);
     // Check that a point column exists.
     $points = $this->table->get_columns('point');
     if (empty($points)) {
         // @TODO Show error.
         return;
     }
     $point_col = array_shift($points);
     $this->point_col_name = $point_col->get_name();
     // Apply filters.
     $filter_param = isset($args['filter']) ? $args['filter'] : array();
     $this->table->add_filters($filter_param);
     $this->table->add_filter($this->point_col_name, 'not empty', '');
 }