/**
   * The HTTP <a
   * href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Link_prefetching_FAQ#As_a_server_admin.2C_can_I_distinguish_prefetch_requests_from_normal_requests.3F">{@code
   * Purpose}</a> header field name.
   *
   * @since 28.0
   */
  public static final String PURPOSE = "Purpose";
  /**
   * The HTTP <a

  }

  // Overriding to mark it Nullable
  @Override
  @CheckForNull
  public abstract V get(@CheckForNull Object key);

  /**
   * {@inheritDoc}
   *
   * <p>See <a
   * href="https://developer.android.com/reference/java/util/Map.html#getOrDefault%28java.lang.Object,%20V%29">{@code
   * Map.getOrDefault}</a>.
   *
   * @since 23.5 (but since 21.0 in the JRE <a

   * nullness checker can already "prove" are non-null. That means that the first parameter to
   * checkNotNull *should* be annotated to require it to be non-null.
   *
   * However, for a variety of reasons, Google developers have written a ton of code over the past
   * decade that assumes that they can use checkNotNull for non-precondition checks. I had hoped to