def harmonic_oscillator_to_xv(actions, angles, potential):
    """
    Transform the input action-angle coordinates to cartesian
    position and velocity for the Harmonic Oscillator potential.

    .. note::

        This function is included as a method of the
        :class:`~gala.potential.HarmonicOscillatorPotential`
        and it is recommended to call
        :meth:`~gala.potential.HarmonicOscillatorPotential.phase_space()` instead.

    Parameters
    ----------
    actions : array_like
    angles : array_like
    potential : Potential
    """
    raise NotImplementedError(
        'Implementation not supported until working with angle-action variables has a better API.'
        )
