question: public boolean functionAvailable ( String ns , String funcName ) throws javax . xml . transform . TransformerException { try { if ( funcName == null ) { String fmsg = XSLMessages . createXPATHMessage ( XPATHErrorResources . ER_ARG_CANNOT_BE_NULL , new Object [ ] { "Function Name" } ) ; throw new NullPointerException ( fmsg ) ; } javax . xml . namespace . QName myQName = new QName ( ns , funcName ) ; javax . xml . xpath . XPathFunction xpathFunction = resolver . resolveFunction ( myQName , 0 ) ; if ( xpathFunction == null ) { return false ; } return true ; } catch ( Exception e ) { return false ; } }
target:  Is the extension function available?