public Builder mergeAnnotation(
          com.google.devtools.cloudtrace.v2.Span.TimeEvent.Annotation value) {
        if (annotationBuilder_ == null) {
          if (valueCase_ == 2
              && value_
                  != com.google.devtools.cloudtrace.v2.Span.TimeEvent.Annotation
                      .getDefaultInstance()) {
            value_ =
                com.google.devtools.cloudtrace.v2.Span.TimeEvent.Annotation.newBuilder(
                        (com.google.devtools.cloudtrace.v2.Span.TimeEvent.Annotation) value_)
                    .mergeFrom(value)
                    .buildPartial();
          } else {
            value_ = value;
          }
          onChanged();
        } else {
          if (valueCase_ == 2) {
            annotationBuilder_.mergeFrom(value);
          } else {
            annotationBuilder_.setMessage(value);
          }
        }
        valueCase_ = 2;
        return this;
      }
<pre>
Text annotation with a set of attributes.
</pre>

<code>.google.devtools.cloudtrace.v2.Span.TimeEvent.Annotation annotation = 2;</code>
java-trace/proto-google-cloud-trace-v2/src/main/java/com/google/devtools/cloudtrace/v2/Span.java