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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def insert_top(self, node):
 """Insert statements at the top of the function body. Note that multiple calls to `insert_top` will result in the statements being prepended in that order; this is different behavior from `prepend`. Args: node: The statement to prepend. Raises: ValueError: If the given node is not a statement. """

    if not isinstance(node, grammar.STATEMENTS):
      raise ValueError
    self.to_insert_top.append(node)