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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def load_backends_and_plugins(plugins, working_set, backends, build_configuration=None):
 """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`). """

  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