code: func FilterLogger(outputLogger log.Logger, predicate func(keyvals []interface{}) bool) log.Logger {
  	return log.LoggerFunc(func(keyvals ...interface{}) error {
  		// Always forward signals
  		if structure.Signal(keyvals) != "" || !predicate(keyvals) {
  			return outputLogger.Log(keyvals...)
  		}
  		return nil
  	})
  }
docs: // Filter logger allows us to filter lines logged to it before passing on to underlying
  // output logger
  // Creates a logger that removes lines from output when the predicate evaluates true