Expanded class hierarchy of Suggester in Search API Solr 4.x
- class \Drupal\search_api_solr\Plugin\search_api_autocomplete\suggester\Suggester extends \Drupal\search_api_autocomplete\Suggester\SuggesterPluginBase implements PluginFormInterface uses \Drupal\search_api\Plugin\PluginFormTrait, BackendTrait