About ||||| (pipe or vertical bars) In yad --form --button

During Working with yad --form displayed some |||(vertical bars) after clicked a button, what are this bars indicating & how I can STOP them to display? Providing sample code, You can experience yad --width=400 --height=200 --button="gtk-ok" --form --field="Click Down":LBL "echo Clicked" --field="Click HERE":BTN Result output will be " **Clicked** *then* **||**