public Builder clearMessageEvent() {
        if (messageEventBuilder_ == null) {
          if (valueCase_ == 3) {
            valueCase_ = 0;
            value_ = null;
            onChanged();
          }
        } else {
          if (valueCase_ == 3) {
            valueCase_ = 0;
            value_ = null;
          }
          messageEventBuilder_.clear();
        }
        return this;
      }
<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