/**
  * @return \yii\db\ActiveQuery
  */
 public function getFile()
 {
     return $this->hasOne(Files::className(), ['id' => 'file_id']);
 }
 public function getFirstfile()
 {
     return $this->hasMany(Files::className(), ['id' => 'file_id'])->viaTable('{{%file_tag_relationships}}', ['tag_id' => 'id'], function ($query) {
         return $query->orderBy('sort');
     })->limit(1);
 }