docs: def find_page_of_state_m(self, state_m):
          """Return the identifier and page of a given state model
  
          :param state_m: The state model to be searched
          :return: page containing the state and the state_identifier
          """
          for state_identifier, page_info in list(self.tabs.items()):
              if page_info['state_m'] is state_m:
                  return page_info['page'], state_identifier
          return None, None