code: public static AccessTokenSource getSource(Bundle bundle) {
          Validate.notNull(bundle, "bundle");
          if (bundle.containsKey(TokenCachingStrategy.TOKEN_SOURCE_KEY)) {
              return (AccessTokenSource) bundle.getSerializable(TokenCachingStrategy.TOKEN_SOURCE_KEY);
          } else {
              boolean isSSO = bundle.getBoolean(TokenCachingStrategy.IS_SSO_KEY);
              return isSSO ? AccessTokenSource.FACEBOOK_APPLICATION_WEB : AccessTokenSource.WEB_VIEW;
          }
      }
docs: Gets the cached enum indicating the source of the token from the Bundle.
  
  @param bundle
  A Bundle in which the enum was stored.
  @return enum indicating the source of the token
  
  @throws NullPointerException if the passed in Bundle is null