public Builder setStartTime(com.google.protobuf.Timestamp value) {
      if (startTimeBuilder_ == null) {
        if (value == null) {
          throw new NullPointerException();
        }
        startTime_ = value;
      } else {
        startTimeBuilder_.setMessage(value);
      }
      bitField0_ |= 0x00000002;
      onChanged();
      return this;
    }
<pre>
The start time of the operation.
</pre>

<code>.google.protobuf.Timestamp start_time = 2;</code>
java-visionai/proto-google-cloud-visionai-v1/src/main/java/com/google/cloud/visionai/v1/IndexAssetMetadata.java