toy_potential = gd.fit_isochrone(w)
toy_actions,toy_angles,toy_freqs = toy_potential.action_angle(w)
fig,ax = plt.subplots(1,1,figsize=(5,5))
ax.plot(toy_angles[0], toy_angles[2], linestyle='none', marker=',')
ax.set_xlim(0,2*np.pi)
ax.set_ylim(0,2*np.pi)
ax.set_xlabel(r"$\theta_1$ [rad]")
ax.set_ylabel(r"$\theta_3$ [rad]")
fig.tight_layout()