code: protected function getSearchFacets(SessionInterface $session) {
  		$facets = $session->get($this->getSessionPrefix() . '_facets', false);
  		return $facets ? \json_decode($facets, true) : $this->getDefaultFacets();
  	}
docs: Fetches the searched facets from the session object
  
  @param SessionInterface $session
  @return string[string][]