code: def mean_absolute_error(y_true, y_pred):
      return np.abs(y_pred - y_true)
  
file_path: adversarial-robustness-toolbox/tests/estimators/regression/test_blackbox.py
imports: import pytest
  import numpy
  from art.estimators.regression import BlackBoxRegressor
  from art.config import ART_NUMPY_DTYPE
  from tests.utils import ARTTestException
label_desc: Use image node_id 1 for calling a global function with example usage: mean_absolute_error(y_true, y_pred) and returns: np