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