docs: def _on_key_pressed(self, event):
          """
          Override key press to select the current scope if the user wants
          to deleted a folded scope (without selecting it).
          """
          delete_request = event.key() in [QtCore.Qt.Key_Backspace,
                                           QtCore.Qt.Key_Delete]
          if event.text() or delete_request:
              cursor = self.editor.textCursor()
              if cursor.hasSelection():
                  # change selection to encompass the whole scope.
                  positions_to_check = cursor.selectionStart(), cursor.selectionEnd()
              else:
                  positions_to_check = (cursor.position(), )
              for pos in positions_to_check:
                  block = self.editor.document().findBlock(pos)
                  th = TextBlockHelper()
                  if th.is_fold_trigger(block) and th.is_collapsed(block):
                      self.toggle_fold_trigger(block)
                      if delete_request and cursor.hasSelection():
                          scope = FoldScope(self.find_parent_scope(block))
                          tc = TextHelper(self.editor).select_lines(*scope.get_range())
                          if tc.selectionStart() > cursor.selectionStart():
                              start = cursor.selectionStart()
                          else:
                              start = tc.selectionStart()
                          if tc.selectionEnd() < cursor.selectionEnd():
                              end = cursor.selectionEnd()
                          else:
                              end = tc.selectionEnd()
                          tc.setPosition(start)
                          tc.setPosition(end, tc.KeepAnchor)
                          self.editor.setTextCursor(tc)