@java.lang.Override
    public void writeTo(com.google.protobuf.CodedOutputStream output) throws java.io.IOException {
      if (((bitField0_ & 0x00000001) != 0)) {
        output.writeMessage(1, getTime());
      }
      if (valueCase_ == 2) {
        output.writeMessage(
            2, (com.google.devtools.cloudtrace.v2.Span.TimeEvent.Annotation) value_);
      }
      if (valueCase_ == 3) {
        output.writeMessage(
            3, (com.google.devtools.cloudtrace.v2.Span.TimeEvent.MessageEvent) value_);
      }
      getUnknownFields().writeTo(output);
    }
<pre>
An event describing a message sent/received between Spans.
</pre>

<code>.google.devtools.cloudtrace.v2.Span.TimeEvent.MessageEvent message_event = 3;</code>
java-trace/proto-google-cloud-trace-v2/src/main/java/com/google/devtools/cloudtrace/v2/Span.java