code: def move(self, item, new_index):
          
          idx = self._items.index(item)
          if idx != new_index:
              item = self._items.pop(idx)
              self._items.insert(new_index, item)
docs: Move an item to the given position.
  
          >>> u = Unique(['spam', 'eggs'])
          >>> u.move('spam', 1)
          >>> u
          Unique(['eggs', 'spam'])
  
          >>> u.move('ham', 0)
          Traceback (most recent call last):
              ...
          ValueError: 'ham' is not in list