def METHOD_NAME(ax, means, covs, color=None, sigma=3):
    ''' Set specific color to show edges, otherwise same with facecolor.'''
    ellipses = []
    for i in range(len(means)):
        eigvals, eigvecs = np.linalg.eig(covs[i])
        axis = np.sqrt(eigvals) * sigma
        slope = eigvecs[1][0] / eigvecs[1][1]
        angle = 180.0 * np.arctan(slope) / np.pi
        ellipses.append(Ellipse(means[i, 0:2], axis[0], axis[1], angle=angle))
    ax.add_collection(PatchCollection(ellipses, edgecolors=color, linewidth=1))