code: public boolean isModified()
      {
          gatekeeper.signIn();
          try
          {
              for (ChangeStack<String> stack : properties.values())
              {
                  if (stack.isModified())
                  {
                      return true;
                  }
              }
  
              return false;
          }
          finally
          {
              gatekeeper.signOut();
          }
      }
docs: Determine whether or not any property has been modified since the last
  load or save.
  
  @return <code>true</code> if any property known to this instance has been
  modified since the last load or save; <code>false</code>
  otherwise