public Builder clearTraceId() {
        traceId_ = getDefaultInstance().getTraceId();
        bitField0_ = (bitField0_ & ~0x00000001);
        onChanged();
        return this;
      }
<pre>
The `[TRACE_ID]` for a trace within a project.
</pre>

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

@return This builder for chaining.
java-trace/proto-google-cloud-trace-v2/src/main/java/com/google/devtools/cloudtrace/v2/Span.java