PyQGIS_loading_files_applying_styles.py

        path_shp = "F:\\Tutorials\\Layout_plot_qgis\\periphereies (1)\\periphereies\\periphereies.shp"
        prefectures = QgsVectorLayer(path_shp, 'prefectures', 'ogr')
        prefectures.loadNamedStyle(style_prefecture_path)
        
        if not prefectures.isValid():
            print("Layer failed to load!")
        else:
            QgsProject.instance().addMapLayer(prefectures)

        individual_prefecture = QgsVectorLayer(filepath, filename_without_extension, 'ogr')
        if not individual_prefecture.isValid():
            print("Layer failed to load!")
        else:
            QgsProject.instance().addMapLayer(individual_prefecture)
        individual_prefecture.loadNamedStyle(style_indiv_prefecture_path)