*
   * <p>A collection is considered immutable if:
   *
   * <ol>
   *   <li>All its mutation methods result in UnsupportedOperationException, and do not change the
   *       underlying contents.
   *   <li>All methods that return objects that can indirectly mutate the collection throw
   *       UnsupportedOperationException when those mutators are called.
   * </ol>
   *
   * @param collection the presumed-immutable collection

   *
   * <p>A collection is considered immutable if:
   *
   * <ol>
   *   <li>All its mutation methods result in UnsupportedOperationException, and do not change the
   *       underlying contents.
   *   <li>All methods that return objects that can indirectly mutate the collection throw
   *       UnsupportedOperationException when those mutators are called.
   * </ol>
   *
   * @param collection the presumed-immutable collection

 *
 * <p>For instance, if <i>steps</i> is 5, one example sequence that will be tested is:
 *
 * <ol>
 *   <li>remove();
 *   <li>hasNext()
 *   <li>hasNext();
 *   <li>remove();
 *   <li>next();
 * </ol>
 *
 * <p>This particular order of operations may be unrealistic, and testing all 3^5 of them may be

   *
   * <ul>
   *   <li>When a {@code ListenableFuture} listener is registered to run under {@code
   *       directExecutor}, the listener can execute in any of three possible threads:
   *       <ol>
   *         <li>When a thread attaches a listener to a {@code ListenableFuture} that's already
   *             complete, the listener runs immediately in that thread.

   * <p>The behaviour of this method is as follows:
   *
   * <ol>
   *   <li>If {@code index >= end}, {@link IndexOutOfBoundsException} is thrown.
   *   <li><b>If the character at the specified index is not a surrogate, it is returned.</b>
   *   <li>If the first character was a high surrogate value, then an attempt is made to read the
   *       next character.
   *       <ol>

   * by the argument according to three criteria:
   *
   * <ol>
   *   <li>The type of the argument is the wildcard or equal to the type of this instance.
   *   <li>The subtype of the argument is the wildcard or equal to the subtype of this instance.
   *   <li>All of the parameters present in the argument are present in this instance.
   * </ol>
   *
   * <p>For example:
   *
   * <pre>{@code

   *          0 thresholdPermits maxPermits
   * </pre>
   *
   * Before going into the details of this particular function, let's keep in mind the basics:
   *
   * <ol>
   *   <li>The state of the RateLimiter (storedPermits) is a vertical line in this figure.
   *   <li>When the RateLimiter is not used, this goes right (up to maxPermits)

 * cause the associated test that generated them to itself fail (which JUnit does not otherwise
 * arrange). The rules for creating such tests are:
 *
 * <ol>
 *   <li>All assertions in code running in generated threads must use the forms {@link #threadFail},
 *       {@link #threadAssertTrue}, {@link #threadAssertEquals}, or {@link #threadAssertNull}, (not

 * <p>There are two entry points for creating a {@code Traverser}: {@link
 * #forTree(SuccessorsFunction)} and {@link #forGraph(SuccessorsFunction)}. You should choose one
 * based on your answers to the following questions:
 *
 * <ol>
 *   <li>Is there only one path to any node that's reachable from any start node? (If so, the graph
 *       to be traversed is a tree or forest even if it is a subgraph of a graph which is neither.)

 * example round-trip using {@link com.google.common.primitives.Doubles#stringConverter}:
 *
 * <ol>
 *   <li>{@code stringConverter().convert("1.00")} returns the {@code Double} value {@code 1.0}
 *   <li>{@code stringConverter().reverse().convert(1.0)} returns the string {@code "1.0"} --
 *       <i>not</i> the same string ({@code "1.00"}) we started with
 * </ol>
 *
 * <p>Note that it should still be the case that the round-tripped and original objects are