docstr: Get the training dataset
  
  Parameters
  ----------
  features
  skip_unreliable
      Whether to skip the unreliable spans in the training set
  
  Returns
  -------
  train_dataset
  num_token_answer_mismatch
  num_unreliable
code: def get_train(self, features, skip_unreliable=True):
      """Get the training dataset
  
      Parameters
      ----------
      features
      skip_unreliable
          Whether to skip the unreliable spans in the training set
  
      Returns
      -------
      train_dataset
      num_token_answer_mismatch
      num_unreliable
      """
      train_dataset = []
      num_token_answer_mismatch = 0
      num_unreliable = 0
      for feature in features:
          if feature.token_answer_mismatch:
              num_token_answer_mismatch += 1
          if feature.unreliable_span:
              num_unreliable += 1
          if skip_unreliable and feature.unreliable_span:
              # Skip when not reliable
              continue
          # Process the feature
          chunk_features = self.process_sample(feature)
          train_dataset.extend(chunk_features)
      return train_dataset, num_token_answer_mismatch, num_unreliable
  
imports: import numpy
  import gluonnlp.data.batchify
  import collections
  import dataclasses
  import mxnet
  from mxnet import np, npx
  from mxnet.gluon import nn
  from mxnet.gluon.nn import HybridBlock
  from dataclasses import dataclass
  from tqdm import tqdm
  from typing import Optional, List, Tuple
  from gluonnlp.data.tokenizers import BaseTokenizerWithVocab
  from gluonnlp.utils.preprocessing import match_tokens_with_char_spans
  from gluonnlp.layers import get_activation
  from gluonnlp.op import select_vectors_by_position
  from gluonnlp.attention_cell import masked_logsoftmax, masked_softmax
  import string
  import re
  import json
label_desc: Use image node_id 3 for calling the SquadDatasetProcessor obj's underlying member method code with example usage: obj.get_train(features, skip_unreliable) and returns: train_dataset,  num_token_answer_mismatch,  num_unreliable