return nil
}

// Step takes a string provided from a server (or just an empty string for the
// very first conversation step) and attempts to move the authentication
// conversation forward.  It returns a string to be sent to the server or an
// error if the server message is invalid.  Calling Step after a conversation
// completes is also an error.

 *   <li>{@link UnmodifiableIterator}
 *   <li>{@link UnmodifiableListIterator}
 * </ul>
 *
 * <h2>Forwarding collections</h2>
 *
 * We provide implementations of collections that forward all method calls to a delegate collection
 * by default. Subclasses can override one or more methods to implement the decorator pattern. For
 * an example, see {@link ForwardingCollection}.
 *
 * <h2>Other</h2>
 *

 * 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
 * invoke methods, they invoke methods on the {@code ForwardingExecutorService}.
 *

 * 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
 * invoke methods, they invoke methods on the {@code ForwardingBlockingQueue}.
 *
 * @author Raimundo Mirisola

 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. The {@link
 * #delegate()} method must be overridden to return the instance being decorated.
 *
 * <p>This class does <i>not</i> forward the {@code hashCode} and {@code equals} methods through to
 * the backing object, but relies on {@code Object}'s implementation. This is necessary to preserve

				Code:           "LambdaFunctionStatusError",
				HTTPStatusCode: http.StatusBadRequest,
				Description:    err.Error(),
			}, r.URL)
			return
		}
	}

	// Set all the relevant lambda forward headers if found.
	fwdHeadersToS3(resp.Header, w)

	if apiErr := fwdStatusToAPIError(statusCode, resp); apiErr != nil {
		writeErrorResponse(ctx, w, *apiErr, r.URL)
		return
	}

      } catch (IllegalAccessException e) {
        throw new RuntimeException(e);
      } catch (InvocationTargetException e) {
        throw Throwables.propagate(e.getCause());
      }
      assertEquals("Failed to forward to " + method, 1, called.get());
    }

    @Override
    public String toString() {
      return "dummy " + interfaceType.getSimpleName();
    }
  }

  @Override
  public NavigableMap<K, V> descendingMap() {
    return new DescendingMap();
  }

  private final class DescendingMap extends Maps.DescendingMap<K, V> {
    @Override
    NavigableMap<K, V> forward() {
      return AbstractNavigableMap.this;
    }

    @Override
    Iterator<Entry<K, V>> entryIterator() {
      return descendingEntryIterator();
    }
  }

 * 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
 * invoke methods, they invoke methods on the {@code ForwardingMultimap}.
 *
 * @author Robert Konigsberg

 * 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
 * invoke methods, they invoke methods on the {@code ForwardingMultimap}.
 *
 * @author Robert Konigsberg