output a shape/net to gds format

 ***** output a shape/net to gds format *****
DRC CHECK MAP "rule_check" GDSII "layer number" "datatype" "filename"
i.e.
Grow_Metal1 { @ Grow metal1 by 0.1u
        SIZE metal1 BY 0.1
    }
DRC CHECK MAP Grow_Metal1 GDSII 21 0 "./mask/grown_m1.gds"

i.e.
LAYER metal metal1 metal2 metal3 // define layer set "metal"
Plot_RESET { @ Output all metal shapes beloging to RESET net
        NET metal RESET
    }
DRC CHECK MAP Plot_RESET GDSII 1 0 "./plots/RESET.gds"