old_contents: from PyQt5.QtCore import QObject
  
  
  class MainWindowModel(QObject):
      """
      The model of Navigation component
      """
  
      def __init__(self, parent, app):
          super().__init__(parent)
          self.app = app
  
      def load_plugins(self, main_window):
          for plugin in self.app.plugins_dir.plugins:
              if plugin.imported:
                  plugin.module.plugin_exec(self.app, main_window)
          if self.app.plugins_dir.with_plugin:
              self.app.plugins_dir.with_plugin.module.plugin_exec(self.app, main_window)
  
new_contents: from PyQt5.QtCore import QObject
  
  
  class MainWindowModel(QObject):
      """
      The model of Navigation component
      """
  
      def __init__(self, parent, app):
          super().__init__(parent)
          self.app = app
  
      def load_plugins(self, main_window):
          for plugin in self.app.plugins_dir.plugins:
              if plugin.imported:
                  plugin.module.plugin_exec(self.app, main_window)
          if self.app.plugins_dir.with_plugin and self.app.plugins_dir.with_plugin.module:
              self.app.plugins_dir.with_plugin.module.plugin_exec(self.app, main_window)
  
subject: Fix error #701