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

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)