Save matplotlib plot to a file.

        Args:
            filename: Filename to write to.
            img_format: Image format to use. Defaults to EPS.

def save_plot(self, filename, img_format="eps", **kwargs):
        """
        Save matplotlib plot to a file.

        Args:
            filename: Filename to write to.
            img_format: Image format to use. Defaults to EPS.
        """
        plt = self.get_plot(**kwargs)
        plt.savefig(filename, format=img_format)