code: public function getTagValues($asString = false)
      {
          if ($this->_tagsList === null && !$this->owner->getIsNewRecord()) {
              // the list of tags is not initialized
              $this->_tagsList = [];
              // trying to obtain related models
              $relation = $this->owner->getRelation('tagsList', false);
              if ($relation instanceof ActiveQuery) {
                  $this->_tagsList = array_unique($relation->select('text')->column());
              }
          }
          return $asString === true ? implode(',', $this->_tagsList) : $this->_tagsList;
      }
docs: Get tags list
  @param bool $asString sign get a list of tags as string
  @return string[]|string