docs: def close_page(self, state_identifier, delete=True):
          """Closes the desired page
  
          The page belonging to the state with the specified state_identifier is closed. If the deletion flag is set to
          False, the controller of the page is stored for later usage.
  
          :param state_identifier: Identifier of the page's state
          :param delete: Whether to delete the controller (deletion is necessary if teh state is deleted)
          """
          # delete old controller references
          if delete and state_identifier in self.closed_tabs:
              self.destroy_page(self.closed_tabs[state_identifier])
              del self.closed_tabs[state_identifier]
  
          # check for open page of state
          if state_identifier in self.tabs:
              page_to_close = self.tabs[state_identifier]['page']
              current_page_id = self.view.notebook.page_num(page_to_close)
              if not delete:
                  self.closed_tabs[state_identifier] = self.tabs[state_identifier]
              else:
                  self.destroy_page(self.tabs[state_identifier])
              del self.tabs[state_identifier]
              # Finally remove the page, this triggers the callback handles on_switch_page
              self.view.notebook.remove_page(current_page_id)