Stata does not provide Pseudo R2 when I run hackman two stage model, could anyone help me how to generate r square or pseudo r square? the current code I have:

/*two steps*/
heckman donat_amount age_diff education_diff , select (donate=age_diff education_diff age_diff education_diff ) twostep
/* default prediction linear predictor*/
margins,dydx(*)
/*marginal effect for probit model can use in Heckman -heckman postestimation*/
margins,dydx(*) predict (psel)

if I want to get marginal effect for both of the stage, am I right for the code above?

Thank you!