def on_config_inited(app, config):
extension_paths = config["<STR_LIT>"] or [<EOL>"<STR_LIT>"<EOL>]<EOL>app.uqbar_book_extensions = []<EOL>for extension_path in extension_paths:<EOL><INDENT>module_name, _, class_name = extension_path.rpartition("<STR_LIT:.>")<EOL>module = importlib.import_module(module_name)<EOL>extension_class = getattr(module, class_name)<EOL>extension_class.setup_sphinx(app)<EOL>app.uqbar_book_extensions.append(extension_class)<EOL><DEDENT>
Hooks into Sphinx's ``config-inited`` event.