private LuceneAnalysisConfig.Analysis analysisConfig(AnalyzerKey analyzerKey) {
        LuceneAnalysisConfig.Analysis analysis = config.analysis(analyzerKey.languageCodeAndStemMode());
        return (null != analysis) ? analysis : config.analysis(analyzerKey.languageCode());
    }
First, checks if more specific (language + stemMode) analysis is configured.
Second, checks if analysis is configured only for a languageCode.
lucene-linguistics/src/main/java/com/yahoo/language/lucene/AnalyzerFactory.java