code: def wr_pydot_dag(self, fout_img, dag):
          
          img_fmt = os.path.splitext(fout_img)[1][1:]
          dag.write(fout_img, format=img_fmt)
          self.log.write("  {GO_USR:>3} usr {GO_ALL:>3} GOs  WROTE: {F}\n".format(
              F=fout_img,
              GO_USR=len(self.gosubdag.go_sources),
              GO_ALL=len(dag.obj_dict['nodes'])))
docs: Plot using the pydot graphics engine.