code: def resolve_none(self, data):
      # replace None to '_'
      for tok_idx in range(len(data)):
          for feat_idx in range(len(data[tok_idx])):
              if data[tok_idx][feat_idx] is None:
                  data[tok_idx][feat_idx] = "_"
      return data
  
imports: import random
  import numpy
  import os
  from collections import Counter
  import logging
  import torch
  import stanza.models.common.seq2seq_constant
  from stanza.models.common.data import map_to_ids, get_long_tensor, get_float_tensor, sort_all
  from stanza.models.lemma.vocab import Vocab, MultiVocab
  from stanza.models.lemma import edit
  from stanza.models.common.doc import *
label_desc: Use image node_id 8 for calling the DataLoader obj's underlying member method code with example usage: obj.resolve_none(data) and returns: data