code: def addSubEditor(self, subEditor, isFocusProxy=False):
          
          self.hBoxLayout.insertWidget(len(self._subEditors), subEditor)
          self._subEditors.append(subEditor)
  
          subEditor.installEventFilter(self)
          subEditor.setFocusPolicy(Qt.StrongFocus)
  
          if isFocusProxy:
              self.setFocusProxy(subEditor)
  
          return subEditor
docs: Adds a sub editor to the layout (at the right but before the reset button)
              Will add the necessary event filter to handle tabs and sets the strong focus so
              that events will not propagate to the tree view.
  
              If isFocusProxy is True the sub editor will be the focus proxy of the CTI.