public Builder<T> copyExistingPipeline(String copyExistingPipeline) {
            this.copyExistingPipeline = copyExistingPipeline;
            return this;
        }
copy.existing.pipeline eg. [ { "$match": { "closed": "false" } } ]

<p>An array of JSON objects describing the pipeline operations to run when copying
existing data. This can improve the use of indexes by the copying manager and make
copying more efficient.
inlong-sort/sort-flink/sort-flink-v1.15/sort-connectors/mongodb-cdc/src/main/java/org/apache/inlong/sort/mongodb/MongoDBSource.java