code: def eventFilter(self, watchedObject, event):
          
          if self.comboBox.isEditable() and event.type() == QtCore.QEvent.KeyPress:
              key = event.key()
              if key in (Qt.Key_Delete, Qt.Key_Backspace):
                  if (watchedObject == self._comboboxListView
                      or (watchedObject == self.comboBox
                          and event.modifiers() == Qt.ControlModifier)):
  
                      index = self._comboboxListView.currentIndex()
                      if index.isValid():
                          row = index.row()
                          logger.debug("Removing item {} from the combobox: {}"
                                       .format(row, self._comboboxListView.model().data(index)))
                          self.cti.removeValueByIndex(row)
                          self.comboBox.removeItem(row)
                          return True
  
          # Calling parent event filter, which may filter out other events.
          return super(ChoiceCtiEditor, self).eventFilter(watchedObject, event)
docs: Deletes an item from an editable combobox when the delete or backspace key is pressed
              in the list of items, or when ctrl-delete or ctrl-back space is pressed in the
              line-edit.
  
              When the combobox is not editable the filter does nothing.