| f | class NegExt: | f | class NegExt: | 
             |  |  |  | 
             |     def __neg__(self): |  |     def __neg__(self): | 
            | t |         my_mro = self.__class__.mro() | t |         mro = self.__class__.mro() | 
             |         parent = my_mro[my_mro.index(NegExt) + 1] |  |         parent = mro[mro.index(NegExt) + 1] | 
             |         try: |  |         try: | 
             |             return self.__class__(parent.__neg__(self)) |  |             return self.__class__(parent.__neg__(self)) | 
             |         except Exception: |  |         except Exception: | 
             |             try: |  |             try: | 
             |                 return self.__class__(self[1:-1]) |  |                 return self.__class__(self[1:-1]) | 
             |             except Exception: |  |             except Exception: | 
             |                 return self.__class__(self) |  |                 return self.__class__(self) |