code: def _extend_nocheck(self, iterable):
          
          current_length = len(self)
          list.extend(self, iterable)
          _dict = self._dict
          if current_length is 0:
              self._generate_index()
              return
          for i, obj in enumerate(islice(self, current_length, None),
                                  current_length):
              _dict[obj.id] = i
docs: extends without checking for uniqueness
  
          This function should only be used internally by DictList when it
          can guarantee elements are already unique (as in when coming from
          self or other DictList). It will be faster because it skips these
          checks.