private MongoNamespace getMongoNamespace(BsonDocument changeStreamDocument) {
        BsonDocument ns = changeStreamDocument.getDocument(NAMESPACE_FIELD);

        return new MongoNamespace(
                ns.getString(NAMESPACE_DATABASE_FIELD).getValue(),
                ns.getString(NAMESPACE_COLLECTION_FIELD).getValue());
    }
The task to work for fetching data of MongoDB stream split .
Copy from com.ververica:flink-connector-mongodb-cdc:2.3.0.
inlong-sort/sort-flink/sort-flink-v1.13/sort-connectors/mongodb-cdc/src/main/java/org/apache/inlong/sort/cdc/mongodb/source/reader/fetch/MongoDBStreamFetchTask.java