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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 root(self: BoardT) -> BoardT: """Returns a copy of the root position."""

        if self._stack:
            board = type(self)(None, chess960=self.chess960)
            self._stack[0].restore(board)
            return board
        else:
            return self.copy(stack=False)