class_docstr: SimpleDataSource
  
  Get data from user defined function.
code: def _get_data(self, position):
      return self._get_data_of_generation(position, self._generation)
  
imports: import atexit
  import csv
  import os
  import threading
  from collections import OrderedDict, deque
  from time import sleep
  import numpy
  from nnabla.config import nnabla_config
  from nnabla.logger import logger
  from nnabla.utils.communicator_util import current_communicator
  from six.moves import queue
  from .data_source import DataSource
  from .data_source_loader import FileReader, load
label_desc: Use image node_id 1 for calling the SimpleDataSource obj's underlying member method code with example usage: obj._get_data(position) and returns: self