public static String getLocationFileOfClass(CtClass clazz) {
        final URL location = getLocationUrlOfClass(clazz);
        if (location == null) return null;

        return location.getFile();
    }
Output string like {@code public ScheduledFuture scheduleAtFixedRate(Runnable, long, long, TimeUnit)}
for {@link  java.util.concurrent.ScheduledThreadPoolExecutor#scheduleAtFixedRate}.

@param method method object
@return method signature string
ttl2-compatible/src/main/java/com/alibaba/ttl/threadpool/agent/transformlet/helper/TtlTransformletHelper.java