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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 stack_plot(self, *args, **kwargs):
 """Plot timeseries stacks of existing data see pyam.plotting.stack_plot() for all available options """

        df = self.as_pandas(with_metadata=True)
        ax = plotting.stack_plot(df, *args, **kwargs)
        return ax