+* Aditionally can be used:
+* A key "widget_type". It can have values "combobox" or "radiobuttons".
+* By default it uses "combobox".
+* A key "buttons_dir" which is applicable only for "radiobuttons" mode.
+* It defines direction of radiobuttons layout. it can be "vertical" or "horizontal"
+* Default value is "vertical"