code: @Override
      protected boolean isSelectedMessagesInSessionScope(HttpMessageContainer messageContainer) {
          final Session session = Model.getSingleton().getSession();
          for (HistoryReference historyReference : getSelectedHistoryReferences(messageContainer)) {
              if (historyReference != null && !session.isInScope(historyReference)) {
                  return false;
              }
          }
  
          return true;
      }
docs: Tells whether or not the selected messages of the given message container are in scope.
  <p>
  By default, the selected messages are obtained by calling the method getSelectedHistoryReferences(httpMessageContainer)
  with the given message container as parameter and for each selected message is called the method
  {@code Session#isInScope(HistoryReference)} with the message as parameter.
  </p>
  <p>
  Normally overridden if other implementations of {@code HttpMessageContainer} are supported. Default are
  {@code SingleHistoryReferenceContainer} and {@code SelectableHistoryReferencesContainer}.
  </p>
  
  @param messageContainer the container that will be evaluated
  @return {@code true} if all the selected messages are in scope, {@code false} otherwise.
  @see #isEnableForMessageContainer(MessageContainer)
  @see Session#isInScope(HistoryReference)