class_docstr: Base Data Geneartor
class_docstr_tok: ["Base","Data","Geneartor"]
docstr: batch_fn batch producer
docstr_tok: ["batch_fn","batch","producer"]
code: def batch_fn(self, batch_examples):
      """batch_fn batch producer"""
      raise NotImplementedError("No defined Batch Fn")
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from __future__ import unicode_literals
  from __future__ import absolute_import
  import os
  import sys
  import six
  from io import open
  from collections import namedtuple
  import numpy
  import tqdm
  import paddle
  from pgl.utils import mp_reader
  import collections
  import time
  from pgl.utils.logger import log
  import traceback
label_desc: Use image node_id 2 for calling the BaseDataGenerator obj's underlying member method code with example usage: obj.batch_fn(batch_examples) without return types