Border style and color for QChart

Hello,

I want to add border style and color for a QChart like button, combobox, etc (

Sample with button in CSS:
QPushButton {
background: qlineargradient( x1:0 y1:1, x2:1 y2:0, stop:0 #D5BD9E, stop:1 #B99556);
color: transparent;
border-style: outset;
border-width: 2px;
border-radius: 10px;
border-color: #B99556;
font: bold;
padding: 2px;
font-family: Montserrat-SemiBold;
}

I can round it with the function "m_chart->setBackgroundRoundness(10)" but I didn't find any fucntion to add a border.

Can you help me to find a solution?

Many thanks