code: def on_checked_changed(self, group, checked_id):
          
          d = self.declaration
          if checked_id < 0:
              with self.widget.clearCheck.suppressed():
                  d.checked = None
              return
          else:
              for c in self.children():
                  if c.widget.getId() == checked_id:
                      with self.widget.check.suppressed():
                          d.checked = c.declaration
                      return
docs: Set the checked property based on the checked state
          of all the children