code: public <K, V> CallbackBuilder withMapCallback(final Class<K> keyClass,
                                                    final Class<V> valueClass,
                                                    final Callback<Map<K, V>> callback) {
          this.callback = callback;
          return this;
      }
docs: Builder method to set callback handler that takes a map
  
  @param keyClass   keyClass
  @param valueClass valueClass
  @param callback   callback
  @param <K>        key type
  @param <V>        value type
  @return this