code: def setup_gui(self):
          
          layout = QGridLayout(self)
          layout.setContentsMargins(0, 0, 0, 0)
          layout.addWidget(self.canvas, 0, 1)
          layout.addLayout(self.setup_toolbar(), 0, 3, 2, 1)
  
          layout.setColumnStretch(0, 100)
          layout.setColumnStretch(2, 100)
          layout.setRowStretch(1, 100)
docs: Setup the main layout of the widget.