les:
            color: Color of selected target.
            builtin_name: Menu variable for built-in theme.
            custom_name: Menu variable for custom theme.
            fg_bg_toggle: Toggle for foreground/background color.
                Note: this has no callback.
            theme_source: Selector for built-in or custom theme.
            highlight_target: Menu variable for the highlight tag target.

        Instance Data Attributes:
            theme_elements: Dictionary of tags for text highlighting.
                The key is the display name and the value is a tuple of
                (tag name, display sort order).

        Methods [attachment]:
            load_theme_cfg: Load current highlight colors.
            get_color: Invoke colorchooser [button_set_color].
            set_color_sample_binding: Call set_color_sample [fg_bg_toggle].
            set_highlight_target: set fg_bg_toggle, set_color_sample().
            set_color_sample: Set frame background to target.
            on_new_color_set: Set new color and add option.
            paint_theme_sample: Recolor sample.
            get_new_theme_name: Get from popup.
            create_new: Combine theme with changes and save.
            save_as_new_theme: Save [button_save_custom].
            set_theme_type: Command for [theme_source].
            delete_custom: Activate default [button_delete_custom].
            save_new: Save to userCfg['theme'] (is function).

        Widgets of highlights page frame:  (*) widgets bound to self
            frame_custom: LabelFrame
                (*)highlight_sample: Text
                (*)frame_color_set: Frame
                    (*)button_set_color: Button
                    (*)targetlist: DynOptionMenu - highlight_target
                frame_fg_bg_toggle: Frame
                    (*)fg_on: Radiobutton - fg_bg_toggle
                    (*)bg_on: Radiobutton - fg_bg_toggle
                (*)button_save_custom: Button
            frame_theme: LabelFrame
                theme_type_title: Label
                (*)builtin_theme_on: Radiobutton - theme_source
                (*)custom_theme_on: Radiobutton - theme_source
                (*)builtinlist: DynOptionMenu - builtin_name
                (*)customlist: DynOptionMenu - custom_name
                (*)button_delete_custom: Button
                (*)theme_message: Label
        z