code: def checkState(self, checkState):
          
          logger.debug("checkState setter: {}".format(checkState))
          if checkState == Qt.Checked:
              commonData = True
          elif checkState == Qt.Unchecked:
              commonData = False
          elif checkState == Qt.PartiallyChecked:
              commonData = None
              # This never occurs, see remarks above in the classes' docstring
              assert False, "This never happens. Please report if it does."
          else:
              raise ValueError("Unexpected check state: {!r}".format(checkState))
  
          for child in self.childItems:
              if isinstance(child, BoolCti):
                  child.data = commonData
docs: Sets the data to given a Qt.CheckState (Qt.Checked or Qt.Unchecked).