Print version of GO-DAG for the GO and for GO slims.

def prt_ver(self, prt):
        """Print version of GO-DAG for the GO and for GO slims."""
        if self.ver_list is not None:
            prt.write("# Versions:\n#    {VER}\n\n".format(VER="\n#    ".join(self.ver_list)))