class_docstr: Download data from https://rajpurkar.github.io/SQuAD-explorer/
  Will return tuples of (doc, question, answer, answer_start, has_answer)
class_docstr_tok: ["Download","data","from","https",":","\/\/rajpurkar.github.io\/SQuAD-explorer\/","Will","return","tuples","of","(","doc",",","question",",","answer",",","answer_start",",","has_answer",")"]
code: def __init__(
      self,
      train_filename=None,
      test_filename=None,
      eval_filename=None,
      ignore_impossible=Config.ignore_impossible,
      max_character_length=Config.max_character_length,
      min_overlap=Config.min_overlap,
      delimiter=Config.delimiter,
      quoted=Config.quoted,
      schema=DEFAULT_SCHEMA,
  ):
      super().__init__(schema)
      self.train_filename = train_filename
      self.test_filename = test_filename
      self.eval_filename = eval_filename
      self.ignore_impossible = ignore_impossible
      self.max_character_length = max_character_length
      self.min_overlap = min_overlap
      self.delimiter = delimiter
      self.quoted = quoted
  
imports: import json
  import math
  from random import choice
  from typing import List, Optional
  from pytext.data.sources.data_source import DataSource, generator_property, JSONString, SafeFileWrapper
  from pytext.data.sources.tsv import TSV
  from pytext.utils.file_io import PathManager
  from pytext.utils.path import get_absolute_path
label_desc: Use image node_id 2 to create a new SquadDataSource object from inherited base classes: DataSource with example: obj = SquadDataSource(train_filename, test_filename, eval_filename, ignore_impossible, max_character_length, min_overlap, delimiter, quoted, schema)