code: def test_tt_eval_loss_decreases():
      happy = HappyTextToText("T5", "t5-small")
      args = TTTrainArgs(num_train_epochs=3)
      before_result = happy.eval("../data/tt/train-eval-grammar.csv")
      happy.train("../data/tt/train-eval-grammar.csv", args=args)
      after_result = happy_tt.eval("../data/tt/train-eval-grammar.csv")
  
      assert before_result.loss > after_result.loss
  
file_path: happy-transformer/tests/test_tt.py
imports: import torch
  from happytransformer import HappyTextToText, TTSettings, TTTrainArgs, TTEvalArgs
  from tests import happy_tt
  from tests.run_save_load import run_save_load
label_desc: Use image node_id 8 for calling a global function with example usage: test_tt_eval_loss_decreases() without return types