public Builder clearBuildId() {
      bitField0_ = (bitField0_ & ~0x00000002);
      buildId_ = null;
      if (buildIdBuilder_ != null) {
        buildIdBuilder_.dispose();
        buildIdBuilder_ = null;
      }
      onChanged();
      return this;
    }
<pre>
A unique identifier for the module, usually a hash of its
contents (up to 128 bytes).
</pre>

<code>.google.devtools.cloudtrace.v2.TruncatableString build_id = 2;</code>
java-trace/proto-google-cloud-trace-v2/src/main/java/com/google/devtools/cloudtrace/v2/Module.java