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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def wrplt(self, fout_dir, plt_ext="png"):
 """Write png containing plot of GoSubDag."""

        # 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