* shared state without additional synchronization necessary for visibility to later executions of
 * the life cycle methods.
 *
 * <h3>Usage Example</h3>
 *
 * <p>Here is a sketch of a service which crawls a website and uses the scheduling capabilities to
 * rate limit itself.
 *
 * <pre>{@code
 * class CrawlingService extends AbstractScheduledService {
 *   private Set<Uri> visited;
 *   private Queue<Uri> toCrawl;

            .put("SEC_WEBSOCKET_PROTOCOL", "Sec-WebSocket-Protocol")
            .put("SEC_WEBSOCKET_VERSION", "Sec-WebSocket-Version")
            .put("X_WEBKIT_CSP", "X-WebKit-CSP")
            .put("X_WEBKIT_CSP_REPORT_ONLY", "X-WebKit-CSP-Report-Only")
            .buildOrThrow();
    ImmutableSet<String> uppercaseAcronyms =
        ImmutableSet.of(

            .put("SEC_WEBSOCKET_PROTOCOL", "Sec-WebSocket-Protocol")
            .put("SEC_WEBSOCKET_VERSION", "Sec-WebSocket-Version")
            .put("X_WEBKIT_CSP", "X-WebKit-CSP")
            .put("X_WEBKIT_CSP_REPORT_ONLY", "X-WebKit-CSP-Report-Only")
            .buildOrThrow();
    ImmutableSet<String> uppercaseAcronyms =
        ImmutableSet.of(

      createConstant(APPLICATION_TYPE, "vnd.oasis.opendocument.text");

  /**
   * <a href="https://tools.ietf.org/id/draft-ellermann-opensearch-01.html">OpenSearch</a>
   * Description files are XML files that describe how a website can be used as a search engine by
   * consumers (e.g. web browsers).
   *
   * @since 28.2
   */
  public static final MediaType OPENSEARCH_DESCRIPTION_UTF_8 =

  /**
   * A builder for creating {@code ImmutableSet} instances. Example:
   *
   * <pre>{@code
   * static final ImmutableSet<Color> GOOGLE_COLORS =
   *     ImmutableSet.<Color>builder()
   *         .addAll(WEBSAFE_COLORS)
   *         .add(new Color(0, 191, 255))
   *         .build();
   * }</pre>
   *
   * <p>Elements appear in the resulting set in the same order they were first added to the builder.
   *

   * ("constant lists"). Example:
   *
   * <pre>{@code
   * public static final ImmutableList<Color> GOOGLE_COLORS
   *     = new ImmutableList.Builder<Color>()
   *         .addAll(WEBSAFE_COLORS)
   *         .add(new Color(0, 191, 255))
   *         .build();
   * }</pre>
   *
   * <p>Elements appear in the resulting list in the same order they were added to the builder.
   *

  /**
   * The HTTP nonstandard {@code X-WebKit-CSP} header field name. It was introduced in <a
   * href="https://www.w3.org/TR/2011/WD-CSP-20111129/">CSP v.1</a> and used by the Chrome until
   * version 25. Please, use {@link #CONTENT_SECURITY_POLICY} to pass the CSP.
   *
   * @since 20.0
   */
  public static final String X_WEBKIT_CSP = "X-WebKit-CSP";
  /**

   * ("constant lists"). Example:
   *
   * <pre>{@code
   * public static final ImmutableList<Color> GOOGLE_COLORS
   *     = new ImmutableList.Builder<Color>()
   *         .addAll(WEBSAFE_COLORS)
   *         .add(new Color(0, 191, 255))
   *         .build();
   * }</pre>
   *
   * <p>Elements appear in the resulting list in the same order they were added to the builder.
   *

  /**
   * A builder for creating {@code ImmutableSet} instances. Example:
   *
   * <pre>{@code
   * static final ImmutableSet<Color> GOOGLE_COLORS =
   *     ImmutableSet.<Color>builder()
   *         .addAll(WEBSAFE_COLORS)
   *         .add(new Color(0, 191, 255))
   *         .build();
   * }</pre>
   *
   * <p>Elements appear in the resulting set in the same order they were first added to the builder.
   *