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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 get_dotstr(self):
 """Return a string containing DAG graph in Grpahviz's dot language."""

        dotobj = self.gosubdagplot.get_pydot_graph() # pydot.Dot
        dotstr = dotobj.create_dot()
        return dotstr