def save_image_to_disk(self, filename_1 = None, filename_2 = None):
        """
        creates an image using the scripts plot function and writes it to the disk
        for single plots (plot_type: 'main', 'aux')
            - if no filname provided take default name
        for double plots (plot_type: 'main', 'aux')
            - if no filnames provided take default name
            - if only one filname provided save only the plot for which name is provided
        Args:
            filename_1: filname for figure 1
            filename_2: filname for figure 1

        Returns: None

        """

        def axes_empty(ax):
            """
            takes an axes object and checks if it is empty
            the axes object is considered empty it doesn't contain any of the following:
                - lines
                - images
                - patches
            Returns:

            """

            is_empty = True

            if ax is not None and len(ax)>0:
                for a in ax:
                    if len(a.lines)+len(a.images)+len(a.patches) != 0:
                        is_empty = False


            return is_empty

        # create and save images
        if (filename_1 is None):
            filename_1 = self.filename('-plt1.png')

        if (filename_2 is None):
            filename_2 = self.filename('-plt2.png')


        # windows can't deal with long filenames so we have to use the prefix '\\\\?\\'
        # if len(filename_1.split('\\\\?\\')) == 1:
        #     filename_1 = '\\\\?\\' + filename_1
        # if len(filename_2.split('\\\\?\\')) == 1:
        #     filename_2 = '\\\\?\\' + filename_2

        if os.path.exists(os.path.dirname(filename_1)) is False:
            os.makedirs(os.path.dirname(filename_1))
        if os.path.exists(os.path.dirname(filename_2)) is False:
            os.makedirs(os.path.dirname(filename_2))


        fig_1 = Figure()
        canvas_1 = FigureCanvas(fig_1)

        fig_2 = Figure()
        canvas_2 = FigureCanvas(fig_2)

        self.force_update()

        self.plot([fig_1, fig_2])

        if filename_1 is not None and not axes_empty(fig_1.axes):
            fig_1.savefig(filename_1)
        if filename_2 is not None and not axes_empty(fig_2.axes):
            fig_2.savefig(filename_2)