code: public Builder clear() {
        traceId = null;
        parentId = null;
        id = null;
        kind = null;
        name = null;
        timestamp = 0L;
        duration = 0L;
        localEndpoint = null;
        remoteEndpoint = null;
        if (annotations != null) annotations.clear();
        if (tags != null) tags.clear();
        flags = 0;
        return this;
      }
docs: bit field for timestamp and duration