private OperationType operationTypeFor(SourceRecord record) {
        Struct value = (Struct) record.value();
        return OperationType.fromString(value.getString(MongoDBEnvelope.OPERATION_TYPE_FIELD));
    }
A wrapped output collector which is used to append metadata columns after physical columns.
inlong-sort/sort-flink/sort-flink-v1.15/sort-connectors/mongodb-cdc/src/main/java/org/apache/inlong/sort/mongodb/MongoDBConnectorDeserializationSchema.java