@Override
  public LogItem intercept(LogItem log) {
    if (reject(log)) {
      // Filter this log out.
      return null;
    }
    return log;
  }
{@inheritDoc}

@param log the original log
@return the original log if it is acceptable, or null if it should be filtered out
xlog/src/main/java/com/elvishew/xlog/interceptor/AbstractFilterInterceptor.java