code: def test_mape_error():
      predictions = pd.Series([1.0, 1.0, 1.0])
      targets = pd.Series([2.0, 2.0, 2.0])
      result = mape().eval_fn(predictions, targets, {})
      assert (
          result.aggregate_results["mean_absolute_percentage_error"]
          == 0.5
      )
  
imports: from unittest import mock
  import pandas
  import pytest
  from mlflow.metrics import MetricValue, ari_grade_level, exact_match, f1_score, flesch_kincaid_grade_level, mae, mape, max_error, mse, ndcg_at_k, precision_at_k, precision_score, r2_score, recall_at_k, recall_score, rmse, rouge1, rouge2, rougeL, rougeLsum, toxicity
label_desc: Use image node_id 17 for calling a global function with example usage: test_mape_error() without return types