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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 show_graph(self, format='svg'):
 """ Render this Pipeline as a DAG. Parameters format : {'svg', 'png', 'jpeg'} Image format to render with. Default is 'svg'. """

        g = self.to_simple_graph(AssetExists())
        if format == 'svg':
            return g.svg
        elif format == 'png':
            return g.png
        elif format == 'jpeg':
            return g.jpeg
        else:
            # We should never get here because of the expect_element decorator
            # above.
            raise AssertionError("Unknown graph format %r." % format)