Compute best-fit rotation matrix.

    The best-fit rotation matrix rotates from_coord such that the RMSD
    between the 2 sets of coordinates are minimized after the rotation.

    Parameters
    ----------
    from_coord, to_coord : np.array
        Nx3 coordinate arrays, where N is the number of atoms. The
        from_coord will rotated such that the rotation will minimize
        the RMSD between the rotated from_coord and to_coord.

    Returns
    -------
    np.array
        3x3 rotation matrix

def get_best_fit_rot_mat(from_coord, to_coord):
    """
    Compute best-fit rotation matrix.

    The best-fit rotation matrix rotates from_coord such that the RMSD
    between the 2 sets of coordinates are minimized after the rotation.

    Parameters
    ----------
    from_coord, to_coord : np.array
        Nx3 coordinate arrays, where N is the number of atoms. The
        from_coord will rotated such that the rotation will minimize
        the RMSD between the rotated from_coord and to_coord.

    Returns
    -------
    np.array
        3x3 rotation matrix
    """
    superimpose_inst.set(to_coord.astype('float64'),
                         from_coord.astype('float64'))
    superimpose_inst.run()

    return superimpose_inst.get_rotran()[0].T