code: def on_input_path_textChanged(self):
          
          input_path = self.input_path.text()
          input_not_grid_msg = tr('input file is not .xml')
  
          if input_path and not input_path.endswith('.xml'):
              self.warning_text.add(input_not_grid_msg)
          elif input_path and input_not_grid_msg in self.warning_text:
              self.warning_text.remove(input_not_grid_msg)
  
          if self.use_output_default.isChecked():
              self.get_output_from_input()
          self.update_warning()
docs: Action when input file name is changed.