def plot_ellipse_matplotlib(cov, pos, ax, nstd=2, **kwargs):
    """
    Plot 2d ellipse in 3d using matplotlib backend
    """
    from matplotlib.patches import Ellipse
    from mpl_toolkits.mplot3d import art3d, Axes3D
    ellipse_param, normal = calc_2d_ellipse_properties(cov,nstd)
    ellipse_kwds = merge_keywords(ellipse_param, kwargs)
    ellip = Ellipse(xy=(0,0), **ellipse_kwds)
    ax.add_patch(ellip)

    ellip = pathpatch_2d_to_3d(ellip, normal=normal)
    ellip = pathpatch_translate(ellip,pos)
    return ellip
Plot 2d ellipse in 3d using matplotlib backend