code: public function constructSelectSQL($fields)
      {
          $sql = array();
  
          $sql[] = "SELECT";
  
          $sql[] = "`" . implode("`, `", array_keys($fields)) . "`";
  
          $sql[] = "FROM `" . $this->dbtable . "`";
          $sql[] = "WHERE `" . $this->pk . "` = " . $fields[$this->pk]->getSQL();
  
          return implode(" ", $sql);
      }
docs: Construct the select sql to retrive model from db