How to plot implicit functions (with two variables) in scipy python using matplotlib?

[scidam]

xmin, xmax, ymin, ymax = xdata.min(), xdata.max(), ydata.min(), ydata.max()
g = lambda x, y: func1(res_lsq.x, x, y)**2
X, Y = np.meshgrid(np.linspace(xmin-0.2, xmax+0.2, 1000), np.linspace(ymin-0.2, ymax+0.2, 1000))
Z = g(X, Y)  # heavy computations.... 

# plotting the result 
plt.contourf(X, Y, np.log(Z), levels=[-10,-8])
plt.gca().scatter(xdata, ydata)
plt.colorbar()
plt.show()