Plaxis 2D/3D commands: delete second points of multiple lines

If I want to delete the second points of the selected line, the command line would be:

           del line_1.second

If I want to apply the same command to a list of lines, how is it possible? would it be something like this?
group_1 is a list of lines.

           map group_1 "del" "second"

which shows error:
           Command "del" not available for object "Line_1"