docstr: Test that multiple train files works
  
  Checks for evidence of it working by looking for words from the second file in the vocab
docstr_tok: ["Test","that","multiple","train","files","works","Checks","for","evidence","of","it","working","by","looking","for","words","from","the","second","file","in","the","vocab"]
code: def test_multiple_files(self, tmp_path, wordvec_pretrain_file):
      """
      Test that multiple train files works
  
      Checks for evidence of it working by looking for words from the second file in the vocab
      """
      trainer = self.run_training(
          tmp_path,
          wordvec_pretrain_file,
          [TRAIN_DATA, TRAIN_DATA_2 * 3],
          DEV_DATA,
          extra_args=["--word_cutoff", "3"],
      )
      word_vocab = trainer.vocab["word"]
      assert "of" in word_vocab
      assert "officials" in TRAIN_DATA
      assert "officials" not in word_vocab
  
      assert "	hers	" not in TRAIN_DATA
      assert "	hers	" in TRAIN_DATA_2
      assert "hers" in word_vocab
  
imports: import os
  import pytest
  import torch
  from stanza.models import tagger
  from stanza.models.common import pretrain
  from stanza.models.pos.trainer import Trainer
  from stanza.tests import TEST_WORKING_DIR, TEST_MODELS_DIR
  from stanza.utils.training.common import choose_pos_charlm, build_charlm_args
label_desc: Use image node_id 6 for calling the TestTagger obj's underlying member method code with example usage: obj.test_multiple_files(tmp_path, wordvec_pretrain_file) without return types