code: public static Iterable<ConfigurationPropertySource> get(Environment environment) {
  		Assert.isInstanceOf(ConfigurableEnvironment.class, environment);
  		MutablePropertySources sources = ((ConfigurableEnvironment) environment)
  				.getPropertySources();
  		ConfigurationPropertySourcesPropertySource attached = (ConfigurationPropertySourcesPropertySource) sources
  				.get(ATTACHED_PROPERTY_SOURCE_NAME);
  		if (attached == null) {
  			return from(sources);
  		}
  		return attached.getSource();
  	}
docs: Return a set of {@link ConfigurationPropertySource} instances that have previously
  been {@link #attach(Environment) attached} to the {@link Environment}.
  @param environment the source environment (must be an instance of
  {@link ConfigurableEnvironment})
  @return an iterable set of configuration property sources
  @throws IllegalStateException if not configuration property sources have been
  attached