code: public HttpChallengeFactory lookup(String authScheme) {
          HttpChallengeFactory result;
  
          if (authScheme == null) return null;
  
          result = challengeFactoriesByAuthScheme.get(authScheme);
          if (result == null) {
  
              if (authScheme.startsWith(AUTH_SCHEME_APPLICATION_PREFIX)) {
                  authScheme = authScheme.replaceFirst(AUTH_SCHEME_APPLICATION_PREFIX, "");
              }
  
              result = challengeFactoriesByAuthScheme.get(authScheme);
          }
          return result;
      }
docs: public until unit test is moved