docs: 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)