code: def setup_gui(self):
          
          scrollarea = self.setup_scrollarea()
          up_btn, down_btn = self.setup_arrow_buttons()
  
          self.setFixedWidth(150)
          layout = QVBoxLayout(self)
          layout.setContentsMargins(0, 0, 0, 0)
          layout.setSpacing(0)
          layout.addWidget(up_btn)
          layout.addWidget(scrollarea)
          layout.addWidget(down_btn)
docs: Setup the main layout of the widget.