docs: def _select_word_cursor(self):
          """ Selects the word under the mouse cursor. """
          cursor = TextHelper(self.editor).word_under_mouse_cursor()
          if (self._previous_cursor_start != cursor.selectionStart() and
                  self._previous_cursor_end != cursor.selectionEnd()):
              self._remove_decoration()
              self._add_decoration(cursor)
          self._previous_cursor_start = cursor.selectionStart()
          self._previous_cursor_end = cursor.selectionEnd()