public Builder addBuckets(
        int index, com.google.cloud.storagebatchoperations.v1.BucketList.Bucket value) {
      if (bucketsBuilder_ == null) {
        if (value == null) {
          throw new NullPointerException();
        }
        ensureBucketsIsMutable();
        buckets_.add(index, value);
        onChanged();
      } else {
        bucketsBuilder_.addMessage(index, value);
      }
      return this;
    }
<pre>
Required. List of buckets and their objects to be transformed. Currently,
only one bucket configuration is supported. If multiple buckets are
specified, an error will be returned.
</pre>

<code>
repeated .google.cloud.storagebatchoperations.v1.BucketList.Bucket buckets = 1 [(.google.api.field_behavior) = REQUIRED];
</code>
java-storagebatchoperations/proto-google-cloud-storagebatchoperations-v1/src/main/java/com/google/cloud/storagebatchoperations/v1/BucketList.java