public function addFacetValue($facetName, $facetValue)
    {
        if ($this->getHasFacetValue($facetName, $facetValue)) {
            return $this;
        }

        $facetValues = $this->getActiveFacets();
        $facetValues[] = $facetName . ':' . $facetValue;
        $this->setActiveFacets($facetValues);

        $this->stateChanged = true;
        return $this;
    }