code: public function visit(Criterion $criterion, CriterionVisitor $subVisitor = null)
      {
          $start = $this->getSolrTime($criterion->value[0]);
          $end = isset($criterion->value[1]) ? $this->getSolrTime($criterion->value[1]) : null;
  
          if (($criterion->operator === Operator::LT) ||
               ($criterion->operator === Operator::LTE)) {
              $end = $start;
              $start = null;
          }
  
          return 'content_modification_date_dt:' . $this->getRange($criterion->operator, $start, $end);
      }
docs: Map field value to a proper Solr representation.
  
  @param \eZ\Publish\API\Repository\Values\Content\Query\Criterion $criterion
  @param \EzSystems\EzPlatformSolrSearchEngine\Query\CriterionVisitor $subVisitor
  
  @return string