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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 error(self, error):
 """ set the error """

        # TODO: check length with value?
        # TODO: type checks (similar to value)
        if self.direction not in ['x', 'y', 'z'] and error is not None:
            raise ValueError("error only accepted for x, y, z dimensions")

        if isinstance(error, u.Quantity):
            error = error.to(self.unit).value

        self._error = error