public Builder clearHeartbeat() {
      if (controlCase_ == 1) {
        controlCase_ = 0;
        control_ = null;
        onChanged();
      }
      return this;
    }
<pre>
A server heartbeat.
</pre>

<code>bool heartbeat = 1;</code>

@return This builder for chaining.
java-visionai/proto-google-cloud-visionai-v1/src/main/java/com/google/cloud/visionai/v1/ReceivePacketsControlResponse.java