我做heckman回归如下  但是用esttab输出到表格发现第二阶段没出来？请问怎么办？
heckman car1 $dealx $acqx $industry $yr,select(dualrole=toptier $dealx $acqx $industry $yr) twostep
estimates store car_1
esttab * using "Topic_2.csv",replace cells(b(star fmt(%9.3f)) t(par(( )))) starlevels(* 0.10 ** 0.05 *** 0.01) legend ar2 nonumbers mtitles("CAR 5" "CAR 6") title(Table 6)
estimates drop car_1