code: protected function onClassFound(ScannedPhpClass $subject)
      {
          $class = $subject->getClass();
          $main  = $this->reader->getClassAnnotation($class, Di\DiServiceAnnotation::class);
  
          if ($main instanceof Di\DiServiceAnnotation) {
              // add the service definition
              $definition = $this->provideServiceDefinitionFor(
                  new ServiceDefinitionProvider\Frame($class, $main, DiOptionsCollection::from($this->reader, $class), null)
              );
  
              $this->addServiceDefinition($definition);
          }
      }
docs: Scanner listener for classes that where found
  
  @param ScannedPhpClass $subject