code: def load_backends_and_plugins(plugins, working_set, backends, build_configuration=None):
    
    build_configuration = build_configuration or BuildConfiguration()
    load_build_configuration_from_source(build_configuration, backends)
    load_plugins(build_configuration, plugins or [], working_set)
    return build_configuration
docs: Load named plugins and source backends
  
    :param list<str> plugins: Plugins to load (see `load_plugins`).  Plugins are loaded after
      backends.
    :param WorkingSet working_set: A pkg_resources.WorkingSet to load plugins from.
    :param list<str> backends: Source backends to load (see `load_build_configuration_from_source`).