def setActiveLevels(self, levels):
        """
        Defines the levels for this widgets visible/processed levels.
        
        :param      levels | [<int>, ..]
        """
        self._activeLevels = levels
        tree = self.uiRecordTREE
        tree.setUpdatesEnabled(False)
        tree.blockSignals(True)
        
        for i in tree.topLevelItems():
            if levels and i.record().levelno not in levels:
                i.setHidden(True)
            else:
                i.setHidden(False)
        
        tree.blockSignals(False)
        tree.setUpdatesEnabled(True)