code: def wrplt(self, fout_dir, plt_ext="png"):
          
          # Ex basename
          basename = self.grprobj.get_fout_base(self.ntplt.hdrgo)
          plt_pat = self.get_pltpat(plt_ext)
          fout_basename = plt_pat.format(BASE=basename)
          fout_plt = os.path.join(fout_dir, fout_basename)
          self.gosubdagplot.plt_dag(fout_plt) # Create Plot
          return fout_plt
docs: Write png containing plot of GoSubDag.