apollo-client-config-data/src/main/java/com/ctrip/framework/apollo/config/data/injector/ApolloConfigDataInjectorCustomizer.java/ApolloConfigDataInjectorCustomizer/isRegistered
class ApolloConfigDataInjectorCustomizer:  public static <T> boolean isRegistered(Class<T> type) {
    return INSTANCE_SUPPLIERS.containsKey(type);
  }