code: def select(self, item):
          
          self._on_unselect[self._selected]()
          self.selected().unfocus()
  
          if isinstance(item, int):
              self._selected = item % len(self)
          else:
              self._selected = self.items.index(item)
  
          self.selected().focus()
          self._on_select[self._selected]()
docs: Select an arbitrary item, by possition or by reference.