presto-main/src/main/java/io/prestosql/operator/WorkProcessorPipelineSourceOperator.java/WorkProcessorPipelineSourceOperator/createOperator
class WorkProcessorPipelineSourceOperator:        @Override
        public SourceOperator createOperator(DriverContext driverContext)
        {
            checkState(!closed, "Factory is already closed");
            return new WorkProcessorPipelineSourceOperator(operatorId, driverContext, sourceOperatorFactory, operatorFactories);
        }