code: def prepend(self, node):
      
      if not isinstance(node, grammar.STATEMENTS):
        raise ValueError
      self.to_prepend[-1].appendleft(node)
docs: Prepend a statement to the current statement.
  
      Note that multiple calls to prepend will result in the last statement to be
      prepended to end up at the top.
  
      Args:
        node: The statement to prepend.
  
      Raises:
        ValueError: If the given node is not a statement.