code: def extend(self, collection):
          
          l_ids = set([a.Id for a in self])
          for acces in collection:
              if not acces.Id in l_ids:
                  list.append(self,acces)
                  info = collection.get_info(Id=acces.Id)
                  if info:
                      self.infos[acces.Id] = info
docs: Merges collections. Ensure uniqueness of ids