code: def test_tc_train_effectiveness_multi():
      before_loss = happy_tc_3.eval(
          "../data/tc/train-eval-multi.csv"
      ).loss
      happy_tc_3.train("../data/tc/train-eval-multi.csv")
      after_loss = happy_tc_3.eval(
          "../data/tc/train-eval-multi.csv"
      ).loss
      assert after_loss < before_loss
  
file_path: happy-transformer/tests/test_tc.py
imports: from happytransformer import HappyTextClassification, TCTrainArgs, TCEvalArgs, TCTestArgs
  from tests.run_save_load import run_save_load
  from pytest import approx
  import pytest
  from tests import happy_tc, happy_tc_3
label_desc: Use image node_id 6 for calling a global function with example usage: test_tc_train_effectiveness_multi() without return types