code: public function one($db = null)
      {
          $row = parent::one($db);
          if ($row !== false) {
              $models = $this->populate([$row]);
              return reset($models) ?: null;
          }
  
          return null;
      }
docs: Executes query and returns a single row of result.
  @param Connection|null $db the DB connection used to create the DB command.
  If `null`, the DB connection returned by [[modelClass]] will be used.
  @return ActiveRecord|array|null a single row of query result. Depending on the setting of [[asArray]],
  the query result may be either an array or an ActiveRecord object. `null` will be returned
  if the query results in nothing.