code: def append(self, obj):
          
          h = self.func(obj)
  
          self.list.append(obj)
          idx = len(self.list) - 1
          self.dict[h] = idx
  
          return idx
docs: Appends C{obj} to this index.
  
          @note: Uniqueness is not checked
          @return: The reference to C{obj} in this index.