Create a QMainWindow instance containing this plugin.

def create_window(self):
        """Create a QMainWindow instance containing this plugin."""
        self.undocked_window = window = PluginWindow(self)
        window.setAttribute(Qt.WA_DeleteOnClose)
        icon = self.get_plugin_icon()
        if is_text_string(icon):
            icon = self.get_icon(icon)
        window.setWindowIcon(icon)
        window.setWindowTitle(self.get_plugin_title())
        window.setCentralWidget(self)
        window.resize(self.size())
        self.refresh_plugin()

        self.dockwidget.setFloating(False)
        self.dockwidget.setVisible(False)

        window.show()