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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 add_main_variation(self, move: chess.Move, *, comment: str = "") -> "GameNode": """ Creates a child node with the given attributes and promotes it to the main variation. """

        node = self.add_variation(move, comment=comment)
        self.variations.remove(node)
        self.variations.insert(0, node)
        return node