code: def create_plugin_layout(tools_layout, main_widget=None):
      
      layout = QVBoxLayout()
      layout.setContentsMargins(0, 0, 0, 0)
      spacing = calc_tools_spacing(tools_layout)
      if spacing is not None:
          layout.setSpacing(spacing)
  
      layout.addLayout(tools_layout)
      if main_widget is not None:
          layout.addWidget(main_widget)
      return layout
docs: Returns a layout for a set of controls above a main widget. This is a
      standard layout for many plugin panes (even though, it's currently
      more often applied not to the pane itself but with in the one widget
      contained in the pane.
  
      tools_layout: a layout containing the top toolbar
      main_widget: the main widget. Can be None, if you want to add this
          manually later on.