SampleElements<Entry<K, V>> mapEntries(SampleElements<K> keys, SampleElements<V> values) {
    return new SampleElements<>(
        mapEntry(keys.e0(), values.e0()),
        mapEntry(keys.e1(), values.e1()),
        mapEntry(keys.e2(), values.e2()),
        mapEntry(keys.e3(), values.e3()),
        mapEntry(keys.e4(), values.e4()));
  }

  public E e0() {
    return e0;
  }

  public E e1() {

So:

```Python
q: Union[str, None] = Query(default=None)
```

...makes the parameter optional, with a default value of `None`, the same as:

```Python

        final Collection<String> values = queryMap.values();
        if (values.stream().anyMatch(s -> s.startsWith(filetypeField))) {
            final ResourceBundle resources = ResourceBundle.getBundle("fess_label", Locale.ENGLISH);
            final String[] fileTypes = ComponentUtil.getFileTypeHelper().getTypes();
            for (final String fileType : fileTypes) {
                final String value = filetypeField + ":" + fileType;

    Set<K> ks = keySet;
    return (ks != null) ? ks : (keySet = new KeySet(this));
  }

  Collection<V> values;

  @Override
  public Collection<V> values() {
    // does not impact recency ordering
    Collection<V> vs = values;
    return (vs != null) ? vs : (values = new Values(this));
  }

  Set<Entry<K, V>> entrySet;

  @Override
  public Set<Entry<K, V>> entrySet() {

   * Object[])} comparator when comparing a value outside the set of values it can compare.
   * Extending {@link ClassCastException} may seem odd, but it is required.
   */
  static class IncomparableValueException extends ClassCastException {
    final Object value;

    IncomparableValueException(Object value) {
      super("Cannot compare value: " + value);
      this.value = value;
    }

  /**
   * Returns the unique greatest value of type {@code C} that is less than {@code value}, or {@code
   * null} if none exists. Inverse operation to {@link #next}.
   *
   * @param value any value of type {@code C}
   * @return the greatest value less than {@code value}, or {@code null} if {@code value} is {@code
   *     minValue()}
   */
  @CheckForNull
  public abstract C previous(C value);

  /**

  @Override
  K checkKey(K key) {
    return checkNotNull(key);
  }

  @Override
  V checkValue(V value) {
    return checkNotNull(value);
  }

  /**
   * @serialData the key class, value class, number of entries, first key, first value, second key,
   *     second value, and so on.
   */
  @GwtIncompatible // java.io.ObjectOutputStream
  private void writeObject(ObjectOutputStream stream) throws IOException {

  @Override
  K checkKey(K key) {
    return checkNotNull(key);
  }

  @Override
  V checkValue(V value) {
    return checkNotNull(value);
  }

  /**
   * @serialData the key class, value class, number of entries, first key, first value, second key,
   *     second value, and so on.
   */
  @GwtIncompatible // java.io.ObjectOutputStream
  private void writeObject(ObjectOutputStream stream) throws IOException {

/**
 * Implementation of {@link Multimap} using hash tables.
 *
 * <p>The multimap does not store duplicate key-value pairs. Adding a new key-value pair equal to an
 * existing key-value pair has no effect.
 *
 * <p>Keys and values may be null. All optional multimap methods are supported, and all returned
 * views are modifiable.
 *

  /**
   * Stores a collection of values with the same key, replacing any existing values for that key.
   *
   * <p>Because a {@code SortedSetMultimap} has unique sorted values for a given key, this method
   * returns a {@link SortedSet}, instead of the {@link java.util.Collection} specified in the
   * {@link Multimap} interface.
   *
   * <p>Any duplicates in {@code values} will be stored in the multimap once.
   */