* element, or at the end of the list if {@code nextSibling} is null. Note: if {@code nextSibling}
   * is specified, it MUST be for a node for the same {@code key}!
   */
  @CanIgnoreReturnValue
  private Node<K, V> addNode(
      @ParametricNullness K key, @ParametricNullness V value, @Nullable Node<K, V> nextSibling) {
    Node<K, V> node = new Node<>(key, value);
    if (head == null) { // empty list
      head = tail = node;

                stream(baseTags).of(stream -> stream.forEach(tag -> popularWordsRequestBuilder.addTag(tag)));
                stream(baseRoles).of(stream -> stream.forEach(role -> popularWordsRequestBuilder.addRole(role)));
                stream(baseFields).of(stream -> stream.forEach(field -> popularWordsRequestBuilder.addField(field)));

      }
      ImmutableIntArray iia = builder.build();
      for (int j = 0; j < iia.length(); j++) {
        assertThat(iia.get(j)).isEqualTo(j);
      }
    }
  }

  private enum BuilderOp {
    ADD_ONE {
      @Override
      void doIt(ImmutableIntArray.Builder builder, AtomicInteger counter) {
        builder.add(counter.getAndIncrement());
      }
    },
    ADD_ARRAY {
      @Override

      ImmutableDoubleArray iia = builder.build();
      for (int j = 0; j < iia.length(); j++) {
        assertThat(iia.get(j)).isEqualTo((double) j);
      }
    }
  }

  private enum BuilderOp {
    ADD_ONE {
      @Override
      void doIt(ImmutableDoubleArray.Builder builder, AtomicInteger counter) {
        builder.add(counter.getAndIncrement());
      }
    },
    ADD_ARRAY {
      @Override

      ImmutableLongArray iia = builder.build();
      for (int j = 0; j < iia.length(); j++) {
        assertThat(iia.get(j)).isEqualTo((long) j);
      }
    }
  }

  private enum BuilderOp {
    ADD_ONE {
      @Override
      void doIt(ImmutableLongArray.Builder builder, AtomicLong counter) {
        builder.add(counter.getAndIncrement());
      }
    },
    ADD_ARRAY {
      @Override

      ImmutableDoubleArray iia = builder.build();
      for (int j = 0; j < iia.length(); j++) {
        assertThat(iia.get(j)).isEqualTo((double) j);
      }
    }
  }

  private enum BuilderOp {
    ADD_ONE {
      @Override
      void doIt(ImmutableDoubleArray.Builder builder, AtomicInteger counter) {
        builder.add(counter.getAndIncrement());
      }
    },
    ADD_ARRAY {
      @Override

            stream(parameter.getSuggestFields()).of(stream -> stream.forEach(builder::addField));
            roleQueryHelper.build(SearchRequestType.SUGGEST).stream().forEach(builder::addRole);
            builder.setSize(parameter.getNum());
            stream(langs).of(stream -> stream.forEach(builder::addLang));

            stream(parameter.getTags()).of(stream -> stream.forEach(builder::addTag));