scipy.interpolate
scipy.interpolate.SmoothBivariateSpline.get_knots
scipy.interpolate.SmoothBivariateSpline.integral
SmoothBivariateSpline.
get_residual
Return weighted sum of squared residuals of the spline approximation: sum ((w[i]*(z[i]-s(x[i],y[i])))**2,axis=0)