code: def value(self):
          
          if self.kind == 'variable':
              return self.target.variables[self.block.args[0]]
          elif self.kind == 'list':
              return self.target.lists[self.block.args[0]]
docs: Return the :class:`Variable` or :class:`List` to watch.
  
          Returns ``None`` if it's a block watcher.