question: public Object extFunction ( String ns , String funcName , Vector argVec , Object methodKey , ExpressionContext exprContext ) throws javax . xml . transform . TransformerException { Object result = null ; if ( null != ns ) { ExtensionHandler extNS = ( ExtensionHandler ) m_extensionFunctionNamespaces . get ( ns ) ; if ( null != extNS ) { try { result = extNS . callFunction ( funcName , argVec , methodKey , exprContext ) ; } catch ( javax . xml . transform . TransformerException e ) { throw e ; } catch ( Exception e ) { throw new javax . xml . transform . TransformerException ( e ) ; } } else { throw new XPathProcessorException ( XSLMessages . createMessage ( XSLTErrorResources . ER_EXTENSION_FUNC_UNKNOWN , new Object [ ] { ns , funcName } ) ) ; } } return result ; }
target:  Handle an extension function.