@java.lang.Override
    public com.google.protobuf.ByteString getTraceIdBytes() {
      java.lang.Object ref = traceId_;
      if (ref instanceof java.lang.String) {
        com.google.protobuf.ByteString b =
            com.google.protobuf.ByteString.copyFromUtf8((java.lang.String) ref);
        traceId_ = b;
        return b;
      } else {
        return (com.google.protobuf.ByteString) ref;
      }
    }
<pre>
The `[TRACE_ID]` for a trace within a project.
</pre>

<code>string trace_id = 1;</code>

@return The bytes for traceId.
java-trace/proto-google-cloud-trace-v2/src/main/java/com/google/devtools/cloudtrace/v2/Span.java