public boolean isAvailable() {
        return available;
    }
@return {@code true} if server endpoint is available.
returns {@code false} if server endpoint is not avaliable for service.
tika-parsers/tika-parsers-ml/tika-parser-nlp-module/src/main/java/org/apache/tika/parser/ner/grobid/GrobidNERecogniser.java