code: def set_fwd_chunk(self, fwd):
          
          raise NotImplementedError("%s not implemented for %s" % (self.set_fwd_chunk.__func__.__name__,
                                                                   self.__class__.__name__))
docs: Sets the chunk following this chunk in the list of free chunks.
  
          :param fwd: the chunk to follow this chunk in the list of free chunks