* intern(a)} is permitted to return one instance now and a different instance later if the
   * original interned instance was garbage-collected.
   *
   * <p><b>Warning:</b> do not use with mutable objects.
   *
   * @throws NullPointerException if {@code sample} is null
   */
  E intern(E sample);

 * override one or more methods to modify the behavior of the backing collection as desired per the
 * <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *
 * <p><b>Warning:</b> The methods of {@code ForwardingCollection} forward <b>indiscriminately</b> to
 * the methods of the delegate. For example, overriding {@link #add} alone <b>will not</b> change

 * that support Java 1.4 and before. Our library needs to do the bare minimum to accommodate such
 * types, though their use may still require an explicit type parameter and/or warning suppression.
 *
 * @author Kevin Bourrillion
 */
@SuppressWarnings({"ComparableType", "rawtypes"}) // https://github.com/google/guava/issues/989
@GwtCompatible
@ElementTypesAreNonnullByDefault

 * Subclasses should override one or more methods to modify the behavior of the backing multimap as
 * desired per the <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *
 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code
 * default} methods. Instead, it inherits their default implementations. When those implementations

   * iterable}. The iterator's {@code hasNext()} method returns {@code true} until {@code iterable}
   * is empty.
   *
   * <p><b>Warning:</b> Typical uses of the resulting iterator may produce an infinite loop. You
   * should use an explicit {@code break} or be certain that you will eventually remove all the
   * elements.
   *

 * override one or more methods to modify the behavior of the backing map as desired per the <a
 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *
 * <p><b>{@code default} method warning:</b> This class forwards calls to <i>only some</i> {@code
 * default} methods. Specifically, it forwards calls only for methods that existed <a

    private SetView() {} // no subclasses but our own

    /**
     * Returns an immutable copy of the current contents of this set view. Does not support null
     * elements.
     *
     * <p><b>Warning:</b> this may have unexpected results if a backing set of this view uses a
     * nonstandard notion of equivalence, for example if it is a {@link TreeSet} using a comparator

  }

  private static PatternCompiler loadPatternCompiler() {
    return new JdkPatternCompiler();
  }

  private static void logPatternCompilerError(ServiceConfigurationError e) {
    logger.log(Level.WARNING, "Error loading regex compiler, falling back to next option", e);
  }

  private static final class JdkPatternCompiler implements PatternCompiler {
    @Override
    public CommonPattern compile(String pattern) {

 * methods to modify the behavior of the backing map as desired per the <a
 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *
 * <p><b>Warning:</b> The methods of {@code ForwardingMap} forward <i>indiscriminately</i> to the
 * methods of the delegate. For example, overriding {@link #put} alone <i>will not</i> change the

    List<String> temp = new ArrayList<>();
    for (Feature<?> feature : features) {
      Object featureAsObject = feature; // to work around bogus JDK warning
      if (featureAsObject instanceof Enum) {
        Enum<?> f = (Enum<?>) featureAsObject;
        temp.add(f.getDeclaringClass().getSimpleName() + "." + feature);
      } else {
        temp.add(feature.toString());