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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 rotate(self, matrix, tol=1e-3):
 """ Applies a rotation directly, and tests input matrix to ensure a valid rotation. Args: matrix (3x3 array-like):
 rotation matrix to be applied to tensor tol (float):
 tolerance for testing rotation matrix validity """

        matrix = SquareTensor(matrix)
        if not matrix.is_rotation(tol):
            raise ValueError("Rotation matrix is not valid.")
        sop = SymmOp.from_rotation_and_translation(matrix,
                                                   [0., 0., 0.])
        return self.transform(sop)