code: def setup_arrow_buttons(self):
          
          # Get the height of the up/down arrow of the default vertical
          # scrollbar :
          vsb = self.scrollarea.verticalScrollBar()
          style = vsb.style()
          opt = QStyleOptionSlider()
          vsb.initStyleOption(opt)
          vsb_up_arrow = style.subControlRect(
                  QStyle.CC_ScrollBar, opt, QStyle.SC_ScrollBarAddLine, self)
  
          # Setup the up and down arrow button :
          up_btn = up_btn = QPushButton(icon=ima.icon('last_edit_location'))
          up_btn.setFlat(True)
          up_btn.setFixedHeight(vsb_up_arrow.size().height())
          up_btn.clicked.connect(self.go_up)
  
          down_btn = QPushButton(icon=ima.icon('folding.arrow_down_on'))
          down_btn.setFlat(True)
          down_btn.setFixedHeight(vsb_up_arrow.size().height())
          down_btn.clicked.connect(self.go_down)
  
          return up_btn, down_btn
docs: Setup the up and down arrow buttons that are placed at the top and
          bottom of the scrollarea.