code: @Nonnull
      public static <T> T
              checkNotNull(Optional<T> object, @Nonnull String message) {
          if (object == null || !object.isPresent()) {
              throw new IllegalArgumentException(message);
          }
          return verifyNotNull(object.get());
      }
docs: check for absent and throw IllegalArgumentException if null or absent
  
  @param object
  reference to check
  @param message
  message for the illegal argument exception
  @param <T>
  reference type
  @return the input reference if not null
  @throws IllegalArgumentException
  if object is null