private com.google.protobuf.SingleFieldBuilderV3<
            com.google.cloud.storagebatchoperations.v1.BucketList,
            com.google.cloud.storagebatchoperations.v1.BucketList.Builder,
            com.google.cloud.storagebatchoperations.v1.BucketListOrBuilder>
        getBucketListFieldBuilder() {
      if (bucketListBuilder_ == null) {
        if (!(sourceCase_ == 19)) {
          source_ = com.google.cloud.storagebatchoperations.v1.BucketList.getDefaultInstance();
        }
        bucketListBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.cloud.storagebatchoperations.v1.BucketList,
                com.google.cloud.storagebatchoperations.v1.BucketList.Builder,
                com.google.cloud.storagebatchoperations.v1.BucketListOrBuilder>(
                (com.google.cloud.storagebatchoperations.v1.BucketList) source_,
                getParentForChildren(),
                isClean());
        source_ = null;
      }
      sourceCase_ = 19;
      onChanged();
      return bucketListBuilder_;
    }
<pre>
Specifies a list of buckets and their objects to be transformed.
</pre>

<code>.google.cloud.storagebatchoperations.v1.BucketList bucket_list = 19;</code>
java-storagebatchoperations/proto-google-cloud-storagebatchoperations-v1/src/main/java/com/google/cloud/storagebatchoperations/v1/Job.java