Generate flow graph in the DOT language and plot it with matplotlib.

        Args:
            ax: matplotlib :class:`Axes` or None if a new figure should be created.
            figsize: matplotlib figure size (None to use default)
            dpi: DPI value.
            fmt: Select format for output image

        Return: matplotlib Figure

def graphviz_imshow(self, ax=None, figsize=None, dpi=300, fmt="png", **kwargs):
        """
        Generate flow graph in the DOT language and plot it with matplotlib.

        Args:
            ax: matplotlib :class:`Axes` or None if a new figure should be created.
            figsize: matplotlib figure size (None to use default)
            dpi: DPI value.
            fmt: Select format for output image

        Return: matplotlib Figure
        """
        graph = self.get_graphviz(**kwargs)
        graph.format = fmt
        graph.attr(dpi=str(dpi))
        #print(graph)
        _, tmpname = tempfile.mkstemp()
        path = graph.render(tmpname, view=False, cleanup=True)
        ax, fig, _ = get_ax_fig_plt(ax=ax, figsize=figsize, dpi=dpi)
        import matplotlib.image as mpimg
        ax.imshow(mpimg.imread(path, format="png")) #, interpolation="none")
        ax.axis("off")

        return fig