code: public function visit(Criterion $criterion, CriterionVisitor $subVisitor = null)
      {
          /** @var \eZ\Publish\API\Repository\Values\Content\Query\Criterion\Value\MapLocationValue $location */
          $location = $criterion->valueData;
          $criterion->value = (array)$criterion->value;
  
          $searchFields = $this->getSearchFields(
              $criterion,
              $criterion->target,
              $this->fieldTypeIdentifier,
              $this->fieldName
          );
  
          if (empty($searchFields)) {
              throw new InvalidArgumentException(
                  '$criterion->target',
                  "No searchable fields found for the given criterion target '{$criterion->target}'."
              );
          }
  
          $queries = array();
          foreach ($criterion->value as $value) {
              foreach ($searchFields as $name => $fieldType) {
                  $queries[] = sprintf('geodist(%s,%F,%F):%s', $name, $location->latitude, $location->longitude, $value);
              }
          }
  
          return '(' . implode(' OR ', $queries) . ')';
      }
docs: Map field value to a proper Solr representation.
  
  @throws \eZ\Publish\Core\Base\Exceptions\InvalidArgumentException If no searchable fields are found for the given criterion target.
  
  @param \eZ\Publish\API\Repository\Values\Content\Query\Criterion $criterion
  @param \EzSystems\EzPlatformSolrSearchEngine\Query\CriterionVisitor $subVisitor
  
  @return string