private void maybeForceBuilderInitialization() {
      if (com.google.protobuf.GeneratedMessageV3.alwaysUseFieldBuilders) {
        getStackFramesFieldBuilder();
      }
    }
<pre>
A call stack appearing in a trace.
</pre>

Protobuf type {@code google.devtools.cloudtrace.v2.StackTrace}
java-trace/proto-google-cloud-trace-v2/src/main/java/com/google/devtools/cloudtrace/v2/StackTrace.java