docs: def _cursor_down(self, value):
          """
          Moves the cursor down by ``value``.
          """
          self._cursor.clearSelection()
          if self._cursor.atEnd():
              self._cursor.insertText('\n')
          else:
              self._cursor.movePosition(self._cursor.Down, self._cursor.MoveAnchor, value)
          self._last_cursor_pos = self._cursor.position()