code: public com.google.protobuf.Duration getRetryDelay() {
      return retryDelay_ == null ? com.google.protobuf.Duration.getDefaultInstance() : retryDelay_;
    }
docs: <pre>
  Clients should wait at least this long between retrying the same request.
  </pre>
  
  <code>.google.protobuf.Duration retry_delay = 1;</code>