docs: def topLevelWindows(self):
          """
          Returns a list of the top level windows for this application.
          
          :return     [<QtGui.QMainWindow>, ..]
          """
          out = []
          clean = []
          for ref in self._topLevelWindows:
              window = ref()
              if window is not None:
                  clean.append(ref)
                  out.append(window)
  
          self._topLevelWindows = clean
          return out