yii\db\ActiveQuery::prepare PHP Method

    public function prepare($builder)
    {
        // NOTE: because the same ActiveQuery may be used to build different SQL statements
        // (e.g. by ActiveDataProvider, one for count query, the other for row data query,
        // it is important to make sure the same ActiveQuery can be used to build SQL statements
        // multiple times.
        if (!empty($this->joinWith)) {
            $this->buildJoinWith();
            $this->joinWith = null;
            // clean it up to avoid issue https://github.com/yiisoft/yii2/issues/2687
        }
        if (empty($this->from)) {
            /* @var $modelClass ActiveRecord */
            $modelClass = $this->modelClass;
            $tableName = $modelClass::tableName();
            $this->from = [$tableName];
        }
        if (empty($this->select) && !empty($this->join)) {
            list(, $alias) = $this->getQueryTableName($this);
            $this->select = ["{$alias}.*"];
        }
        if ($this->primaryModel === null) {
            // eager loading
            $query = Query::create($this);
        } else {
            // lazy loading of a relation
            $where = $this->where;
            if ($this->via instanceof self) {
                // via junction table
                $viaModels = $this->via->findJunctionRows([$this->primaryModel]);
                $this->filterByModels($viaModels);
            } elseif (is_array($this->via)) {
                // via relation
                /* @var $viaQuery ActiveQuery */
                list($viaName, $viaQuery) = $this->via;
                if ($viaQuery->multiple) {
                    $viaModels = $viaQuery->all();
                    $this->primaryModel->populateRelation($viaName, $viaModels);
                } else {
                    $model = $viaQuery->one();
                    $this->primaryModel->populateRelation($viaName, $model);
                    $viaModels = $model === null ? [] : [$model];
                }
                $this->filterByModels($viaModels);
            } else {
                $this->filterByModels([$this->primaryModel]);
            }
            $query = Query::create($this);
            $this->where = $where;
        }
        if (!empty($this->on)) {
            $query->andWhere($this->on);
        }
        return $query;
    }

 public function prepare($builder)
 {
     if ($this->type !== null) {
         $this->andWhere(['type' => $this->type]);
     }
     return parent::prepare($builder);
 }