@java.lang.Override
      public boolean hasMessageEvent() {
        return valueCase_ == 3;
      }
<pre>
An event describing a message sent/received between Spans.
</pre>

<code>.google.devtools.cloudtrace.v2.Span.TimeEvent.MessageEvent message_event = 3;</code>

@return Whether the messageEvent field is set.
java-trace/proto-google-cloud-trace-v2/src/main/java/com/google/devtools/cloudtrace/v2/Span.java