<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _on_changed(self):

 """Slot for changed events"""

        page = self._get_page()
        if not page.flag_autosave:
            page.flag_changed = True
            self._update_gui_text_tabs()