private com.google.protobuf.SingleFieldBuilderV3<
              com.google.devtools.cloudtrace.v2.Span.TimeEvent.Annotation,
              com.google.devtools.cloudtrace.v2.Span.TimeEvent.Annotation.Builder,
              com.google.devtools.cloudtrace.v2.Span.TimeEvent.AnnotationOrBuilder>
          getAnnotationFieldBuilder() {
        if (annotationBuilder_ == null) {
          if (!(valueCase_ == 2)) {
            value_ =
                com.google.devtools.cloudtrace.v2.Span.TimeEvent.Annotation.getDefaultInstance();
          }
          annotationBuilder_ =
              new com.google.protobuf.SingleFieldBuilderV3<
                  com.google.devtools.cloudtrace.v2.Span.TimeEvent.Annotation,
                  com.google.devtools.cloudtrace.v2.Span.TimeEvent.Annotation.Builder,
                  com.google.devtools.cloudtrace.v2.Span.TimeEvent.AnnotationOrBuilder>(
                  (com.google.devtools.cloudtrace.v2.Span.TimeEvent.Annotation) value_,
                  getParentForChildren(),
                  isClean());
          value_ = null;
        }
        valueCase_ = 2;
        onChanged();
        return annotationBuilder_;
      }
<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