private com.google.protobuf.SingleFieldBuilderV3<
              com.google.protobuf.Duration,
              com.google.protobuf.Duration.Builder,
              com.google.protobuf.DurationOrBuilder>
          getHeartbeatIntervalFieldBuilder() {
        if (heartbeatIntervalBuilder_ == null) {
          heartbeatIntervalBuilder_ =
              new com.google.protobuf.SingleFieldBuilderV3<
                  com.google.protobuf.Duration,
                  com.google.protobuf.Duration.Builder,
                  com.google.protobuf.DurationOrBuilder>(
                  getHeartbeatInterval(), getParentForChildren(), isClean());
          heartbeatInterval_ = null;
        }
        return heartbeatIntervalBuilder_;
      }
<pre>
The maximum duration of server silence before the client determines the
server unreachable.

The client must either receive a `Packet` or a heart beat message before
this duration expires; otherwise, the client will automatically cancel
the current connection and retry.
</pre>

<code>.google.protobuf.Duration heartbeat_interval = 5;</code>
java-visionai/proto-google-cloud-visionai-v1/src/main/java/com/google/cloud/visionai/v1/ReceivePacketsRequest.java