public Object getAt(final String key) {
            Object result;
            if (matcher != null && (result = matcher.group(key)) != null) {
                return result;
            }
            if (map != null && (result = map.get(key)) != null) {
                return result;
            }
            if (extraLog != null && (result = getField(extraLog, key)) != null) {
                return result;
            }
            if (log != null && (result = getField(log, key)) != null) {
                return result;
            }
            return null;
        }
Set the log container to store the final log if it should be persisted in storage,
if no container is set, the final log will be sent to source receiver,
if log container is set, the log is only stored in the container, and won't be sent to source receiver.

@param container the log container
oap-server/analyzer/log-analyzer/src/main/java/org/apache/skywalking/oap/log/analyzer/dsl/Binding.java