code: def add_item(self, item, replace = False):
          
          if item.jid in self._jids:
              if replace:
                  self.remove_item(item.jid)
              else:
                  raise ValueError("JID already in the roster")
          index = len(self._items)
          self._items.append(item)
          self._jids[item.jid] = index
docs: Add an item to the roster.
  
          This will not automatically update the roster on the server.
  
          :Parameters:
              - `item`: the item to add
              - `replace`: if `True` then existing item will be replaced,
                otherwise a `ValueError` will be raised on conflict
          :Types:
              - `item`: `RosterItem`
              - `replace`: `bool`