## Add extra information { #add-extra-information }

You can declare extra information in `Field`, `Query`, `Body`, etc. And it will be included in the generated JSON Schema.

You will learn more about adding extra information later in the docs, when learning to declare examples.

/// warning

Extra keys passed to `Field` will also be present in the resulting OpenAPI schema for your application.

   * designed for this nonstandard interaction will use it. As of 2019-01, the only widely-used
   * implementation of this pattern is [gRPC][grpc].
   *
   * Because the encoding of interleaved data is not well-defined for HTTP/1, duplex request
   * bodies may only be used with HTTP/2. Calls to HTTP/1 servers will fail before the HTTP request

   *
   * @param finalizableReferenceClass FinalizableReference.class.
   * @param queue a reference queue that the thread will poll.
   * @param frqReference a phantom reference to the FinalizableReferenceQueue, which will be queued
   *     either when the FinalizableReferenceQueue is no longer referenced anywhere, or when its
   *     close() method is called.
   */

   *
   * <ul>
   *   <li>If {@code count} is 0, {@code mean} may have any finite value (its only usage will be to
   *       get multiplied by 0 to calculate the sum), and the other parameters may have any values
   *       (they will not be used).
   *   <li>If {@code count} is 1, {@code sumOfSquaresOfDeltas} must be exactly 0.0 or {@link
   *       Double#NaN}.
   * </ul>
   */

   *
   * <p><b>Performance note:</b> When feasible, {@code initialCapacity} should be the exact number
   * of values that will be added, if that knowledge is readily available. It is better to guess a
   * value slightly too high than slightly too low. If the value is not exact, the {@link
   * ImmutableIntArray} that is built will very likely occupy more memory than strictly necessary;
   * to trim memory usage, build using {@code builder.build().trimmed()}.

   *     no effect on the multimap.
   */
  @CanIgnoreReturnValue
  Collection<V> replaceValues(@ParametricNullness K key, Iterable<? extends V> values);

  /**
   * Removes all values associated with the key {@code key}.
   *
   * <p>Once this method returns, {@code key} will not be mapped to any values, so it will not

 * @author Joshua O'Madadhain
 * @param <N> The most general node type this builder will support. This is normally {@code Object}
 *     unless it is constrained by using a method like {@link #nodeOrder}, or the builder is
 *     constructed based on an existing {@code ValueGraph} using {@link #from(ValueGraph)}.
 * @param <V> The most general value type this builder will support. This is normally {@code Object}

* @method\n * @memberof Popper.Utils\n * @param {Object} position - CSS position the Popper will get applied\n * @param {HTMLElement} popper - the popper element\n * @param {Object} referenceOffsets - the reference offsets (the popper will be relative to this)\n * @param {String} placement - one of the valid placement options\n * @returns {Object} popperOffsets - An object containing the offsets which will be applied to the popper\n */\nexport default function getPopperOffsets(popper, referenceOffsets,...

  /**
   * Returns {@code x}, rounded to a {@code double} with the specified rounding mode. If {@code x}
   * is precisely representable as a {@code double}, its {@code double} value will be returned;
   * otherwise, the rounding will choose between the two nearest representable values with {@code
   * mode}.
   *
   * <p>For the case of {@link RoundingMode#HALF_DOWN}, {@code HALF_UP}, and {@code HALF_EVEN},

 * that every {@code Runnable} that is {@linkplain #add added} will be executed after {@link
 * #execute()} is called. Any {@code Runnable} added after the call to {@code execute} is still
 * guaranteed to execute. There is no guarantee, however, that listeners will be executed in the
 * order that they are added.
 *
 * <p>Exceptions thrown by a listener will be propagated up to the executor. Any exception thrown